just thought I post an answer for someone else. I got a response on the Plexi forum, to raise the value of the reverb pot = better reverb. also you can mess with the input bias resistor. still have to check this out but, if someone is in the same boat as me,(don't like the reverb) you can try this stuff out.
I accidently put a 12AX7 in the reverb driver of a MKIVa. MKIVa's use a 12AT7 for that slot.
Anyways, the reverb was horrible after that. In went a Mullard CV4024 (12AT7) and it was sooo much better. No pedal needed.
Of course, sound is subjective, but I liked the Lee Jackson Mr. Springgy reverb pedal way better than the Holy Grail.
It was quite expensive though.
Good luck!