Their's a difference between determination, and just not knowing what you're getting into. i can assure you unless you have superb fabricating skills, and an equally as awesome bank account balance, this is not worth the time you would put into it.
if your dead set on trying to make it awd which is quite a feat in itself. i suggest you do some searching and find the guys who made the black hatch with the wagovan drivetrain in it running a boosted sohc vtec engine.
and yes you could make more power out of a v6 over a 4 cyl. because quite simply there is two more cylinders. however its just not necessary. There are v8 engines making thousands of horsepower, but in a honda that kind of power just isn't needed, and it would be impossible to get to the ground. it hasn't become popular to move away from the standard 4cyl powerplant, because the 4cyl engines work just fine. built and boosted they make ample horsepower and torque with more then enough mmph to get down the track with 12, 11, and 10 second passes regardless of chassis. also i'm not aware of a transversely mounted awd v6 transmission, but i'd bet if there is one its carrying a hefty pricetag.
I'm saving you a shit ton of trouble right now trust me. just stick with a d,b,or k-series engine. despite the fact that this engine/trans combo literally won't fit in a rex, the money it would cost you to make this happen could be much better spent on a different engine/trans combination, and leave you a much quicker more reliable car at the end of the day.
ninja edit: here is a thread covering the beginning steps to converting a rex to awd with the wagovan drivetrain. many people feel like this is not even worth attempting. imagine how much more difficult an awd v6 conversion would be..
http://www.homemadeturbo.com/forum/index.php?topic=96607.0