So, what are some thoughts on rack mounted reverb units around $100-150 new or used. I use a Marshall 401 DSL and don't really like the reverb in the amp. I use a Roland GP8 multi effects unit in the FX loop and thought a rack mounted reverb might be a good addition.

I have looked at or am thinking about:

Yamaha SPX 90
Alesis Quadraverb

I have read some good things about reverb pedals (holy grail) but I want the reverb after the pre-amp. Unless there are compelling reasons for it in another position.