Your batteries are 8C. Today most LiPoes are 20C or higher. To be able to deliver more current higher "C"-batteries get a weight-penalty because there are more metal in them! As long as you don`t need more than 12A in your setup you could choose a "newer" battery" at only 800mAh rated 20C. But the flighttime will be far less of course. Or take the weight-penalty by buying a 1500mAh battery from the latest generation... Or search for batteries with lower C-ratings. They will weigh less.
Every pilot have their own favourites, and mine is FlightPower LiPo. For me they are the best, but mark the words "for me"
One advice: if you would like to buy new LiPoes stick with one brand, their balancer and so on.
A123 are available as loose cells. Advantage is as mrasmm said: High C-rating, fast charging, and far safer than LiPo. Disadvantage: a bit more weight per mAh, and different voltage. Loose cells here:
http://www.aircraft-world.com/shopexd.asp?id=5041
Interesting dataes:
http://www.aircraft-world.com/prod_d.../A123/A123.pdf