So you're looking for a simple setup? With all that stuff?
Anyways, if you're just looking for a backup to the Peavey I think you've got all that. No need to add a compressor into the mix, especially if you don't use one right now. Just keep in mind, you get what you pay for. I'd rather not play through a comp at all than play through a $40 one, unless it was a KILLER deal on a used piece.
You'll probably get more hits in the Effects forum for recommendations on a comp. Just search around first. There are tons of threads on them.
And yes, you'll need a preamp if you get rid of your current pre (the Boss)...