bluebird and GTiR are FWD and AWD respectivly, so no point fitting them really
S13 blacktop is gonna be a tad more expensive than S13 redtop but are the same motors except the blacktop is newer
Redtop $1895
Blacktop $2095
S14 blacktop has VTC? i think, not sure of the right name but it has variable intake cam timing, and a T28 turbo, puts out 220hp so a bit more than S13 SR20 and also more expensive but newer as well its not as straight as a swap like the S13 one, not sure of the differences though.
Blacktop $2495
S15 blacktop is newest (obviously) puts out about 250hp with T28 ball-bearing turbo, (i think, either way its better than the S14 T28) variable cam w/e but comes with a weaker 6 spd transmission, this one is also gonna be harder to fit in as its from a different model car but you have are pretty mechanically inclined lets say, it shouldn't be too difficult
Blacktop $3250
(all prices from
www.jazzproparts.com, other places will be more/less depending)
why not keep the RB20 and use the $2000 or more you save from not buying a new engine and build it up, put a good response/power turbo on, maybe stronger internals, depending on how much power you want and run with that?
Inline 6 man, unless you want the lighter weight of the SR20?
RB25DET is gonna cost more (obviously) and unless you really want crazy power, an RB20 or SR20 of some kind is gonna give you great response and good power (perfect for drifting), there is a guy making a DVD on how to do the swap, and if you set it far enough back and low enough, it doesn't throw off the weight very much, ie still fells neutral, so its really up to you and your power goals
as well, hopefully you won't leave your Rb20 stock or it isn't, so that will increase torque and do away with your no-torque woes. Either way its all up to you, lets see some pics of that coupe too! =)
hope all this helps!
ttyl
(anyone, please correct me if any of my information is wrong)