the rear exchanger from the SRX is the biggest and provides better cooling. The problem you may have is depending on what long track kit you use the bigger exchanger does not fit. I have the rear SRX exchanger on my piped SXR.
Make sure the extension is long enough so the SRX or stock SXr exchanger doesn't hit the track when compressed. I never had a heating problem with MMax exchanger and they sit flat to the ext running all the mods you mentioned.