You might want to consider a 5-cell Nimh pack. And for a .60 size plane, you'll probably be fine with something in the 1500-2000mah range, depending on how you fly and how many flights you want before recharging.

Now, there's nothing really wrong with putting a Li-Ion/regulator system in a .60 size plane, it's just usually overkill.

If you want a bit of redundancy, you can put a pair of 6v (or 4.8v) Nimh packs in, using two swtiches, and run them to two different ports on the RX. That's the setup I have in my 72" Mosquito. If I loose a switch or battery, I'll have power to land, and it's a simple to put together setup that doesn't cost a ton. Since there are 2 batteries powering the system, a pair of 1200mah cells would do the job (that's a totaly of 2400mah available).

Oh, the brand of the battery really isn't a big deal. The brand of the cell matters more, and even then, it's not that huge of a deal unless you're really pushing the cells. That said, I usually look for Sanyo cells.