Probably one of the best deals for a preamp/compressor is the FMR really nice series. The dual preamp is $500+-. There are two stereo comps ($200-250 and cleaner and ... more colorful), plus the mono pbc (even more color). I haven't used that one but it has a good reputation for a $450 comp.
Cheaper there is the art stuff. Or you can find the dbx 160 for $400 or so new but there are a lot of ebay units out htere - it sounds good on bass. eVen the cheaper 163 sounds good on bass. It has a built in di, or my 163 does.
I don't know if I'd go any cheaper, unless you want to use it for live stuff. Much cheaper and you really are just messing up the sound more than helping.
A Warm Audio and pcb ought to be a very nice chain - one you can keep even after you get better hardware.
@
@