Running Dual channel with unknown brands

Right now I have 512mb PC2100 RAM in my Athlon XP 2800 Barton machine, and I'd like to have 1gb total while running in Dual Channel mode. My mobo is listed in my sig. My 2 options are:

-Buy another 512 stick of PC2100.

or

-Buy 2 512 sticks of PC2700

If I go with the first option, what are the chances that the new module won't run in Dual channel mode with my old stick? It's not a main brand stick. Also, since I'm running a 2800XP, would PC2100 be holding my performance back?

The second option wouldn't be bad, except for the obvious higher cost.

I believe that it is safer to buy sets of ram made by the same manufacturer, etc. to run Dual channel as stated in numerous mobo manuals, etc. Personally, if i were you I'd OC that processor and get PC3200 or PC3500 if you OC high enough. And yes it is possible to OC your processor to the equivalent of a 3200+ with stock cooling. But if you really want to stay with the original two, go with the second.

As long as you know each sticks failure point (max memtest and Prime stable) then mixing sticks isn't a problem.

What your trying to do in buying a match set is get two sticks of mem that perform similar (they will still not be abolutely the same, just close). Its a marketing gimmick in my opinion for dual channel kits.

So if you mix memory (I do and have done) you just have to know what the timings, max FSB, memory ratio, and voltage you can run each memory stick at. Then run in DC with the setting of the mem stick you have that has the lowest FSB, worst timing, highest volts, etc.

Sometimes it works, sometimes it dosent. I ran dual channel with 3 sticks before, 1 512 stick and the other 2 were two 256's. Sometimes sticks just wont run together period, so its a crapshoot.