Combining completely different types of ram?

My old mobo could only hold 2 chips of ram, so when I upd from 2x512 sticks to 2x1024s- I had a gig left over

My question is can my new 4slot mobo take all 4 chips even though theyre 2 diff speeds/sizes?

the mobo:
http://www.newegg.com/Product/Product.asp?item=N82E16813128263

The new ram is 2 of these:
http://www.newegg.com/Product/Product.asp?Item=N82E16820220045

The old ram im not completly sure of the specs atm but its 2ish yrs old

Yes, however all of the RAM will run at the speed of the slowest chip.

so i guess the question is:

2gb @ 3200
or
3gb @ 2700

any insight?

Unless you're doing some intensive 3d modelling or video rendering, I can't think of where you'd benefit having 3 gigs of RAM over 2. I'd go with the faster RAM.