Acro Cub
Hi ravin - I posted some suggestions about power plants etc for the House of Balsa Micro/ Acro/ Cub in another forum - so here it for you.
If you don't want to go the brushless route, I think that a Speed 300 with a 5:1 MP Jet gearbox and an 8x6 would work well.
The problem with the Acro Cub is that, though it is light (only 14oz with the Astro 010), it has a small wing area, and thus high wing loading (12.6oz/sq.ft will require it to fly far faster than typical 5-6oz/sq.ft Slow Flyers). To keep the weight manageable you are going to need a very light motor (yes, the Astro 010 weighs only 2oz complete, but that's $125!). I don't think it will carry a Speed 400 or 400 cobalt well (100+g), but a Speed 300 with 5:1 and 8x6 will give you as much as 13oz thrust on 8amps and weighs only about 70g (2.46oz) - and at $25 for the motor/gearbox and $35 for a Castle Creations Pixie 20 ESC (THE BEST you can get) you're home [relatively] free.
NiCds do charge faster in the field but they also weigh more - so its a trade off (which you will have to weigh up - sorry about that!). With NiCd I'd say you are limited to 7-8 cell 350's, but with NiMH you could go to 8-cell 720's. You could leap into Li-poly for dramatic decrease in weight and increase in mAh and flight time, since they could cope with the 6-8amp draw you'll need with the Speed 300.
Now that's my NZ2 cents-worth - I will be keen to read all the critical comments from the far more intelligent and informed out there!
Cheers, Phil