I also wouldn't shy away from the China variants of LED spotlights, they all ultimately come from there anyways. I've been buying $3 knock-off Cree torchlights to keep around the house and have been very impressed, I can get a pencil beam out to 50m no problem with those things.
Save yourself some money, anything with legitimate Cree LEDs is going to work just fine. I've been looking at going with these on my enclosed trailer & a light bar on the back. I liked the idea of 30 degree lamps to get a little better throw distance, and you could probably pick up three pairs of them cheaper than a single pair of 60 degree. With a decent charged up deep cycle, you should easily see 8+ hours of run time off 108 watts of light.
http://www.amazon.com/Nilight-1260lm-Dr ... +spotlightget-n-birdy makes some excellent points, just lost the ground connection on my trailer for the 3rd time now since I've had it
Also worth noting, I needed to buy the relay for my truck to offer up a trailer charge on the 7 prong. Not sure if that's just a Ford thing, but sure is a bitch when you're trying to troubleshoot lack of voltage. I would not recommend taking a feed direct from the truck battery like fouler suggests, that's just another unneeded invitation for murphy to show up at your party.
Since you'll be all wired up, don't forget to add the radio too - everyone needs a little gangnam style when they're setting up the spread.