[bobkoure]

Originally Posted by opteron_bitch

Well it can't really be compared to a heater core on that list because none of them are of comparable size.

Which was why I was pointing out that frontal area was the most important dimension - so you could take a guess at how they'd compare. If you mean, how would it compare to a heater core of exactly the same size, then I'd have to answer "probably about the same".

To rephrase my question: How well will the dual 80mm black ice radiator and 2 80mm blowers cool (in your opinion)?

I don't really have an opinion on the BIM-II as I've never used one. If someone here actually had experience with one I'd of course defer to them. Failing that, rather than just guessing and pretending that I know what I'm talking about I'm trying to hand you what I know about radiators in general. You'll still end up with a guess - but it will be your guess and you'll understand why it might or might not be a good guess.
So, to over-simplify a bit less than before, radiators work by having air molecules bounce off them - the molecules leave with more energy then they came in with, carrying away heat. You can increase the number of air molecules by increasing the size of the radiator or by increasing the air stream through it. So you can make up for having a small(er) radiator by having more forceful fans.
Also note that a "perfect" radiator would only get coolant down to the same temp as the air going through it. You are penalizing yourself a bit by using case air - and from the top of the case at that.

If you were trying to get maximum performance out of the dual 80mm vents (above the PSU) what radiator/heatercore and fans/blower(s) would you get?

I'd look very closely at other places I could put the radiator. You could mount a large radiator in the top of the case, for instance, put two 80mm fans in those two positions, but blowing in and build a triangular shroud to duct this incoming air to the radiator mounted above (so you're cooling with outside-the-case air, coming in the back and exiting the top - not ideal as you've going to "inhale" some of the heated air coming out of the PSU, but better than using inside air)
If I had to mount a radiator in that 180x160mm space, I'd have to use a BIX micro-II. I'd at least try to duct air from outside the case to the fans.
If I was feeling ambitious, I'd use a blower, and duct inlet air through the top of the case to its inlet - or bolt it to the top of the case and duct to the radiator. Of course, if you spilled coffee into the inlet hole, you'd have it sprayed all over whatever's behind your PC...