Well I have a keeley modded mt-2 and I tried it with my Laney aor pro tube 100 watt and it's the best combination I've heard so far. You realy get that stomach punch. Try to avoid the Marshall jcm 900's. You can find those Laney's pretty cheap on eBay.
Try to pick up a Hughes & Kettner Attax 200, i own one for eleven years now and besides the fact that it never failed me it is truly an awesome sounding transistor amp, i do own a JCM900 too but that Attax rules!