NF7-S v2.0 Dual Channel slot population issue- not the same question that's on here six times, i hop

hello all
I have the aforementioned mb, Abit NF7-S v.2.0, BIOS 1.8
i'm running two sticks of Mushkin 3200 "level II" no issues at 200mhz,
dual channel in slots 3+2, 2-2-2-6 (their SPD)
have a 400fsb Barton 3000+ at 200x11 (2205)
not really trying to push anything too hard, you see... but I've had
some buyer's remorse, wishing i'd waited until i could afford to go
for the full Gig of RAM.

SO, my question is this:
could i just buy an additional 512 MB stick, and fill all three slots,
with the same dual channel performance? i mean, i realize the
overclockability would dive, but i'm not really pushing the fsb-

AND- my instinct would be to put the biggest stick in slot 3, and
the two 256 Meg sticks in slots 1+2, unless somebody knows better?
and would the fact that the RAM is all dual BANK (for an onboard total
of six banks) present another issue? the manual reads as though
that's not a problem...

any feedback welcome! thank you in advance~