SDHC size

[desitdt]

I have just purchased a htc 6800 with alltel and i was wondering what is the maximum size MicroSDHC card that will work with this particular phone. I have contacted Alltel Support and they say it is goes up to 4gb but he told me it may work with a higher capacity card. I have also read posts about the HTC touch with people claiming they have been able to use a 6gb and 8gb on the TOUCH. If higher than 4gb will work, what is the best place to get one. ive found this that is $40 w/shipping:
http://digitalmediaoutlet.com/SanDis...B0012Y2LLE.htm

if not what is the best price for a 4gn card. Ive found this:

http://digitalmediaoutlet.com/Sandisk-4GB-MicroSDHC-Memory-Card-with/M/B000SMVQK8.htm