I bought 2 sets of 4600mAh 2s2p with charger form ebay for $100. I tested these out on a slash but with the lower voltage they did not perform very well. These are now my practice cells.

My 4wd with MMax 5700 runs very good. I can tell they are still slower than a Lipo.

The ones that the OP linked to are older. Only 3.2v
Look for these:

The 18650 cells are 3.3v 1100mAh.

The 26650 cells are 3.3v 2300mAh. Search around and you can get these cheaper by buying a dewalt pack and make your own.

Also note the size of these to make sure they will fit.