downpipe and turbo questions, which to get? Options

[Rollout]

Well it seems as though no one on DSMtuners.com is willing to tackle my questions, so possibly some of u dsm'ers can help me out. Thanks A LOT.
Heres my post:

take all this into consideration when evalutating...
I have a 97 Eclipse GSX with upper and lower i/c piping (greddy), Greddy type-s bov, K&N intake, Apexi N1 catback, walbro 255

ok, at the moment i am looking at finishing off my exhaust system. I already have the Apexi N1 cat back and need to get a downpipe. In the future i plan to upgrade to the big 16g or the evo III b16g. here are my questions.

1. RNR 02 eliminator downpipe in SS is $440 on rnrracing.com, or i can get an evo III O2 housing (does this bolt right on?) for $190 and a apexi downpipe for $207 - thats $397 together, or i can just port my stock O2 housing (id like specifics on how well this works?) and get the Apexi downpipe also. This is all 3" and the downpipes will "remove" the cat.

what are your suggestions?

2. Which turbo? Price differences are minimal (around 500 i think?) but what are the real differences? the Big 16g i know requires a $200 kit for the 2g, im not exactly sure what the evo III b16g requires? i know that the evo has a bigger wheel but thats about it, so more lag, but more power?

thats about it for now... thanks in advance, i know a lot of questions
just dont want to order the wrong thing here.

[awd4kicks]

The piping on my O2 eliminator is 2.5" but the mating flange to the down pipe is 2.25. The RRE "2.5" gasket is just a bit bigger than the flange to boot, so there not much there. This was a hand crafted unit by some schmoe trying to get into the DSM fabrication game. Josh and I have reworked this puppy three times but the flange is a typical purchased unit like those found on RRE's DYI products.