Starkeeper, I guess I am not reading your questions properly.
If you are going to play the sounds on your PSR using Live-Styler or OMB almost any LT will do.
If you are going to play Live-Styler with LiveSynth Pro using the sYnerGIGS Wavetable then any Pentium will do with 256MB plus RAM (Windows XP - 128 MB + Wavetable - 50 MB + programs - xy MB = 256 MB plus).
If you are going to use things like the B4 or Kontakt plus effects (especially reverb) then you should use some thing like a Pentium 4 with 512 MB & 1 GHz. I use a Pentium 4, 1GB RAM, 2GHz and even at that I can bring it down to its knees with heavy doses of effects like reverb.
The sYnerGiGS Wavetable is a GM and Partial GS/XG set of instruments contained in one soundfont file. This file is about 44 or 50 MB in size. It is this file you load into the soft synth LiveSynth Pro and use for playing your styles with Live-Styler or OMB. So you have to connect Live-Styler using something like Midi Yoke (free) to forte/LiveSynth Pro. And then Play!!!