As Phi mentioned, I am currently using 3 par38 bulbs over my 20L tank. It will soon be 4 bulbs, as I just ordered in 2 BoostLed all Royal blue par30's today so I can get that nice flouresent dawn/dusk coloration.
The current bulbs on my tank are:
2 Nanotuners 12k on the left and centre.
1 IceCooLed 10k on the right.
The Nanotuners bulbs have more of a purpley affect to them, which is really nice actually. To my eyes it blends in and looks more natural. The red digitata and tricolor frags I have under them appear to be rather happy with that color combination and are growing.
The IceCooLeds 10k bulb is a little too Yellow to my taste, and it seems the corals under then, with the exception of the lower light acan doesn't like it as much either.
In terms of heat from these lamps.. I can touch them with my bare hand after they have been on for several hours and not burn myself. This heat quickly disipates a couple inches away from the bulb.
Here is a video of my 20L
For a 10g tank, it will really depend on what color you want. I would suggest 2 bulbs for full coverage.
BoostLed has their bulbs on at $70 each right now and they have the most when it comes to color combinations. You would more than likely like the 3blue 2white w/60 degree optics for the 20k look.
For two bulbs shipped to Canada it will be $165usd (which is pretty much on par with our dollar).
RapidLeds new bulbs have amber color in them. I don't know what they look like in person, as I haven't used them, but there are good reviews about them. They are $99 for the 7led bulbs and $75 for the 5led bulbs.
Nanotuners still remains the same with their bulbs.. the 20k and 12k with 40degree optics are on sale right now for $88, but their 60 degree bulbs are still $120.
When my BoostLed bulbs come in I will set them up and take a couple of pics of how they look on their own over the tank, and in combination with 2 of the nanotuners bulbs.