usurper, I experimented in order to find what was the least expensive ESC I could find that would work well. I recommend saving up a few bucks and paying what it takes to get the Castle ESC, that being said...IMHO the "next best" is the Hobbywing ESCs. I don't know if they work well with an Astro, so it could end up being wasted money, YMMV. The Hobby King Turnigy worked "OK", and the generic Chinese ESC didn't have an LVC so it fried my LiPo pack.
does anyone have the link for the tutorial for adding extra capcitors?
The capacitors will have two leads marked "+" and "-". They get soldered onto the red/black power leads going into the ESC. If you aren't paying attention and get them backwards, then after you power up...the caps will pop open and smell bad...two dollars each. Need one cap for a friction drive, maybe two for a BB-drive, and I'd recommend four if you are driving the rear axle (based on what I've read, if you are unsure...more is better).
Here are the two big threads on capacitors, the first link has my recommendations. Caps will arrive in your mailbox in an envelope in less than a week, as I said, two dollars each.http://endless-sphere.com/forums/viewtopic.php?f=30&t=22194&start=45#p382837
Updated Cap choices for high power motor controllers Updated (6-pages)http://endless-sphere.com/forums/viewtopic.php?f=28&t=7504
Castle HV Controllers - Use Extra Caps! (15-pages)