Thanks for the suggestions guys, it looks like I'll be checking my local craigslist regularly and saving up. I'm also looking to add a few more effects, ever since I bought my Source Audio BEF Pro I've been GASing for a Hot Hand (probably not the most useful for most things, but way cool). I'm thinking a good distortion like the MWBD would also be a huge benefit over the built in distortion on the Rumble 350. That and still considering upgrading the electronics in the Rex... so much GAS, so little $$$.

That said, I can't really complain. My current set-up is considerably better than most my age, and its working fine for me now. There's just always something a little better out on TalkBass.
As for older Peavey stuff, I play through some sort of Peavey head and a Hartke 2x10+1x15 combined cab at my church (the church owns the rig). It sounds pretty good to me, although I've never had much time to really figure it out or try it at higher volumes.