The Dual is a nice player with an easy-going sound and it matches well with Ortofon cartridges. As for stylus going up in price, that's the thing with most cartridges today... prices are higher.
Linn K5 or K9 are similar or the AT95E - Highly musical and upfront presentation, but more rough sounding than the relaxed easy going Ortofon. You could try changing the Ortofon to the AT95E, it will work well with the Dual tone arm. Another choice would be the AT-120, this too could spice up your sound. Smooth, detailed but a bit forward.
Or you could try an Ortofon 2M Red or Blue, the 2Ms are more upfront and leaning towards the bright compared to the relaxed and smooth OM-serie. Or something from the Goldring 2x00-serie.
Rega Planar and the Pro-Ject - different thinking. Dual has suspension, the Rega and Pro-Ject does not so needs to be placed upon a solid support. Dual has a smoother tone in itself and works with a wide range of music, a good all-rounder. The Rega or Pro-Ject can be more detailed but instead of the RPM 1.3 I would recommend the Music Hall 2.2 LE. You see, the tonearm in the RPM 1.3 is a bit on the short side, (which means it doesn't track as well as the other Pro-ject tonearms and it also has more distortion) and it has the lowest mass of all Pro-Ject tone arms (partly because it is slightly shorter than the other Pro-Ject tonearm) so suits best with high compliance cartridges. RPM 1.3 is a nice and cheerful entry level turntable, and a solid buy with the 2M Red cat ridge - but there are of course alternatives.. The Music Hall has a Pro-Ject 9 tone arm, which is better than the 8.5 the RPM 1.3 comes with, and the Music Hall comes in various colors too if you want. A nice audiophile start. It's based upon Pro-Ject components but tuned by Roy Hall. Also made in the same factory in the Czech republic that builds turntables for Pro-Ject.
But of course you can buy an oldie but goldie turntable. The Thorens 160 is a classic and many are available 2nd hand. The suspension can need service, but there's plenty of parts available and lots of info on the net available for it so it's one of the best buys of the classic turntable era in the 70's.
Oh and the Thorens 300-serie from the 80's (316, 318, 320 and 321) are also very good with solid plinth, advanced suspension and nice sound. Lenco is also a good solid buy. Those turntables can be more fuzzy and in need of more love than a new entry level turntable, but they can also be more rewarding in the sound. Yes, I do feel that a high class vintage player has the potential of a better sound quality than a new entry level turntable.
You don't mention what you find is wrong with the sound you currently have, it could be helpful if you let us know more clearly what you are after.