if you wanted a cheep upgrade a hx35/40 hybrid would be the way to go. it has fast spoolup and gives you the power and air flow of a hx40. there great little turbos, i ran one for almost ayear towing 20k of hay and it was an awsome little turbo for the $. just recently upgraded to something bigger. as for the hx55 way to slow the hybrid with the hx55 or ht60 would be a good little twin turbo setup, thats what i was going to build.

 

S300G is a good upgrade.