One thing I have not seen mentioned about the cheapy ebay turbo is that it is a T3. There is now way a T3 can flow 25 PSI. They cap out efficiency about 19psi and optimally at 15psi, anything past that is lost to heat and creates extra wear. You can do a T3/T4 hybrid, t3 on the inlet side and t4 on the compressor side, this allows the quicker spool up of the smaller turbo with more volume of a larger compressor side. It will not push 25, but will hold 19-21 with out issue.

to run 25 psi besides all the additional mods that have been mentioned you would want to look at T4 60 trim turbos minimal.