My day gig is with a lighting company (we do installs mostly churches & schools).
The thing to remember about LEDs is that often times you need fewer of them.
2 LED PARs on each side if the stage can give you a lot of light and a lot of color choices. Add something like the 4bar for backlighting (Don't forget backlighting, its really important to give depth) and you can have some pretty decent looks on a 15 - 20' wide stage. The tricky part is controlling them. Even the cheapest RGB (red/green/blue) color-mixing PAR uses 3 DMX channels for control. (DMX is kind of like midi for lights). So 2 on the left, 2 on the right, and 4 in the back means you need at least a 24 channel controller if you want separate control over each light. That's kind of hard to do with a foot controller and if you just set them all to change with the music you don't really know what you're going to get for any given song.
Cool post. Good info. I have 2 banks of 4 regular PAR lights that I have a foot controller for. I now have a line on 4 LED 64 lights for a very reasonable price. I was thinking of picking them up for front lighting and using the 2 x 4s as back light. As you say though the issue is control.