Steve
I think you are very close. (and there are many more opinions on this than just mine)
There are quite a few GTxx setups available but most are not better than 24/18g imo. Here is how I would rank them.
K16
K24
K16 flash
K16 stage 2
K24 flash
k24 stage 4
GT610
K16/16g
GT660
K24/18g
GT700

Of course there is some variability in these rankings depending on individual drivers, flashes, additional equipment, individual cars, many other variables...

what turbos and other components does a GT600 and GT 660 have?

I think that list is pretty accurate, although I think the 18g's should be at the top (or bottom) of the list. I base this statement on 60-130 times and 1/4 mile times/trap speeds. We have a ton of data from 18g cars, and not much from GT700 cars, but based on that data, the 18g is top dog.

where does a k16/24 fall into that list?

Good question...funny how it was left off the list entirely. Below 16/16g and above 18s would be my guess

Based on the 60-130 data seals 16g ran a 7 sec, not sure if there are any 16/24 which ran that fast. So with the available data i would place it above 16g.

While we're discussing K16/16gs, if I sent my stock K16s in for an upgrade (approx. $1000 I keep reading here..), is there any way they can recondition the existing components cheaply? My turbos have over 52k on them at this point, I'd hate to pay for the upgrade and then have them crap out in the not-so-distant future..

When your turbos are in for the upgrade, you will be advised if it is felt you require any additional work.

I'm sure they will condition any problem they might see with your turbo before they return it to you. I can't see them modifying your turbos and overlooking possible problems. They will want your turbos "right" before they return them to you.

Here is a data point for the K16/24 turbo on street tires, full weight, AWD..

John,

That was a fast run (trap speed) for a K16 hybrid. Thanks for the data.

The only time I know of is a 7.93 run by KPG. Thus, I would place them like this:

K16
K24
K16 flash
K16 stage 2
K24 flash
k24 stage 4
GT610
K16/24g
K16/16g
GT660
K24/18g
GT700

Adam,
I dont have much data either for GT700. Only one I can remember is an old 6.6x run by Sean (Dr. Jitsu) before he got the new setup. Can you recall other times? It seems like only recently that 6.6x has become more common with K24/18g setups. I dont know what a Gt700 with all the trimmings would do now. How about EVT700 any data there?

On the list whats a k16 stage 2?

Stage 2 = flash and exhaust