I'll give you a diametrically opposite view to sreten's!
IMO, most speakers like to be "gripped" by ss amps ... but a tube pre can impart the right amount of "tubeyness" to your sound.
However, be aware of slightly confusing terminology ... a preamp
has input source selection and a volume control - and it sometimes includes a phono input (which means that RIAA equalisation and amplification of a MM cartridge's signal is dealt with).
But a "phono pre
" is simply the bit that does the RIAA equalisation and signal amplification - so you need a line-stage (ie. preamp) as well.
In your case, you said your (ss) SX-3700 receiver has a phono input. Without knowing anything specific about the SX-3700, I would suggest its phono stage can only be "ordinary-sounding" ... so the Bellari should deliver a more attractive sound (as well as delivering some nice "tubeyness"!
). However, you may find it delivers more "hiss" than the Pioneer (an inevitable problem with tubes being put into low signal level situations - much more so than with ss phono stages).
Go for it! You'll always be able to sell the Bellari with minimal loss, if you don't like it.