No worries Cube Bass, I hope I've been helpful.
I was thinking a bit about my response after I posted and was wondering myself how important really, is a speed control? If you could pick up an older Debut without that for a good price then that would be a good way to go. Even an essential will probably give you almost all of the performance of a Debut. Most upgrades are fairly subtle - but lots of small upgrades do lead to differences in sound quality. These differences can be improvements but they can also just be different (and expensive).
I'm not sure about the speed fluctuation (i.e. regulated motor) figures. I was using a Technics direct drive that had .025% wow & flutter. So regulated and very, very good figures. Much better than my pro-ject. But I couldn't say it sounded better than the pro-ject. I thought my pro-ject sounded 'better' with the same cartridge. Plus a slightly fast turntable, for argument's example, can sound more 'dynamic'. I've also read that a quartz locked turntable (i.e. 'regulated' like a speed box) can display a 'cogging' effect as the tt is always trying to adjust to correct 33.3 speed ... Others will argue that this is not the case. So I guess my point with speed control is, is that it's not as simple as just saying that a speed box will make a difference that is good to your ears just because you have it. Honestly I wouldn't worry about it.
Lots of tt's have fixed cables. It's not the end of the world but obviously you can't play around with cables if what you've got is soldered onto the end of the TT
. But, really, playing about with cables is to play around with capacitance (i.e the resistance in the cable). I think you can be confident that if Pro-ject spec the cables that you'll be right with any of the Pro-ject phono boxes. Capacitance matters with cartridges as different carts expect different loads and sound more or less bright depending on the load they work best with. It gets pretty technical. That's me saying I'm still learning and I've had a few red wines with dinner tonight
But I believe that OM series cartridges are pretty forgiving of capacitance. Audio Technica cartridges, as an example, are less forgiving and more prone to sounding bright if the capacitance is wrong (i.e. too high). So again, don't worry about it.
Absolutely, you can upgrade even the lowest OM5e with the 10, 20, 30 & 40 (and you can go the other way too - ie. from a 40 stylus down to a 5e). You could also swap stylus' with the Omega cartridge and some other Ortofon Cart bodies as well. Believe it or not there's lower than a 5e. There's a 5 (conical) and a 3e. All are compatible. You'll also see "super" Om bodies - so a Super Om10, 20 etc. Again, these are compatible so any stylus any cartridge will work. These super bodies are a later revision with a slightly different winding of the coils within them and a very slightly different sound - again, think subtle difference.
I'm not very knowledgeable with phono stages. There are really cheap ones that are basically a few dollars worth of capacitors and a case. They feature pretty generic circuit layouts and are usually 2 stages. People tend to state on the internet that 3 stage arrangements sound better. I don't know off hand what those stages are. I was under the impression that all the pro-ject stages were dual mono and quite good compared to the alternatives. Perhaps the cheapest one is worth passing on, but ... Anyway, A lot of people like the Schitt Mani and the Art Pre DJ gets a mention as cheap that punches above it's cost and the >> insert personal choice here << always gets a mention. I've read positive and negative opinions on all the preamps you mention. Sometimes you'd swear it was like the end of the world the way some people talk about any given phono stage. Basically I understand that better phono stages sound more 3 dimensional, more like you are in the room, or provide more lifelike renditions of instruments. Plus, as you've observed, when you start spending more money you can change things like the capacitance and select between MM/MC cartridges. I don't think this last feature will be relevant to you. Overall all the more expensive features you mention allow you to tweak the sound and tailor it to your taste or bring it closer to the set of parameters that the cartridge works best with.
I've never used amplified speakers (i.e. I assume what you have is a pair of speakers with a built in amplifier / volume control?). So I can't speak as to whether they will allow you to hear the differences that a better phono stage might provide.
With phono stages, if you weren't sure then I'd suggest you buy something cheap, get going and then perhaps upgrade when you can test better and hear that it's better. By cheap I mean <$20 US. If it really sucks then you won't be out much and it's a cheap experiment to discover that you can hear the differences that better equipment provides. Just make sure whatever you get has a ground screw for the tt.
Ultimately the sound you achieve can only be as good as the weakest link. That could be any given component or the room or the combination of components that you have in the room that they are housed in. The weakest link could be the setup - a miss-aligned cartridge will never sound good, no matter how expensive the turntable is that it's attached to. The cost to fix that is a single page printed on a printer and the time taken to learn how to get it right. Certainly no one was born knowing how to align cartridges using Baerwald ... (I hope!)
I think whatever you buy will allow you to learn about tt's and their sound and based on that learning your own appreciation of what you want, what sounds good to you, will develop. I say this because I can't see any glaringly bad choices in all the gear you've mentioned. I certainly haven't used most of it but none of it is trash and I think any of it (even an essential with a 5e) would make listening to vinyl enjoyable. Trust me, I'm a stranger on the internet!