I'm not sure about the tprime but my droid 2 I believe can handle upto 32gb sdcard. So you'll be fine with a 32. Check out amazon for sd cards. I just got a 16gb class 10(all class means on sd card is their write/read speed, I think 10 is the highest) for $18.
Sent from my Droid2 running Cm9
yes,32gb is max for sdhc standard. But be careful with class 10, I've had problems with two of them (adata, lexar) in three devices (droid2 global, droid3, Panasonic lumix camera). I had to change them for class 6. (The device had frozen after the screen lit off and waking up, or the card turned to read only in the camera, had to unmount and mount again after each waking up)
So I would recommend you to try the card first, because I guess other people with same cell phone could have no problems with the cards.
Class 6 is slower in usb reader, but the same speed at work.
My Rezound is rocking a 64gig micro SDXC card (Sandisk, Class 6). It works just fine. Only gliitch (and it's annoying, but tolerable) is it forgetting/not seeing my music after a reboot. But it's worth it for the extra storage! Works on most of the new phones. For all I know, that glitch is a SenseUI issue and not an Android issue.