Need suggestions

I have an 01 cummins 5.9 automatic with a stock transmission and its finally startin to slip! I want to get a new transmission or a rebuild kit or something! and start tricking this truck out. I dont want to go crazy with money, but I want something to hold around 450 to 500 horse, any suggestions or prices would be awesome!

a buddy of mine got a full suncoast tranny with converter for around $5800. that was billet shafts new clutches bearings, etc. and a torque converter. i myself just got a full billet, minus the intermediate shaft for my truck from dave goerend (goerend transmission inc. ) for a reasonable $5175. he says you don't need a billet intermediate until around 800-850 horse.

torque converter, valve body, input shaft, billet flex plate should hold 500 hp..

you can find a trust worthy tranny guy and most likely he will be able to get what you need a little cheaper just dont try and get out of buying good parts or used crap and it should be fine had mine done and not any problems with it so far 30,000 so far and i hate to drive easy just remember do it right the frist time and dont worry anymore