My experience with with the hobbico life packs hasn't been very good. It is very hard to detect when they are going bad, it is nearly impossible, and they have an extremely steep discharge curve at the bottom end of their capacity.
I have owned about 10 and have had 3 failures, one of which costed me an airframe.
As for using a BEC, I prefer to stay away from BEC's when possible as they can fail during high current bursts,
().
If you do want to use a BEC, many people like and use the castle CC pro, I loved mine until it exploded mid flight(FYI: I was pushing it
very close to its limits).
If you really want to use a BEC and dont mind spending some money, western robotics makes a very very good bec, the Hercules Super Pro BEC works VERY WELL. A couple guy are using them at my local field and really love them.
http://www.western-robotics.com/hercules-super-BECPRO_hp.html
I personally prefer to run a lipo RX pack when possible, but if you need to run low voltage and dont want to use a regulator or a BEC with a battery then the tail dragger A123 packs are proven to be extremely good and reliable.
IMHO:
The tail dragger 2300 mah A123 packs would be best suited for you.