ballheads ....markins, rrs, etc

I'm looking at getting a new decent, light ballhead. Checked out the markins qball q3.
Is the only thing i need to buy the q3 and a plate? i will be using with a gripped 40d and Velbon EL Carmagne 540A tripod?

I'm looking at the plates, which one i need to get? I'm assuming the larger the plate, the more stability?
Is the quick release on the q3 that little knob on the side? if so, do you push it for the quick release or turn it?

Finally, can anyone think of more bang for the buck with and another ballhead. Looking to spend around $300. I more than likely won't be using anything bigger than my 24-105. Maybe my sigma 70-200 2.8, but that would be pretty rare.

any help is appreciated.

No one makes quality as light as Markins; if you want light, they are the brand to look at. The quick release on Markins is a screw, so you turn the knob. Lots of people here replace it with RRS quick release (and plate/bracket) but I've left mine on. I find it is plenty quick and usable.

Also, consider an L-bracket rather than a plate so you can quickly switch from landscape to portrait without having to use the notch on the ballhead (takes the weight off-center and limits the movement).

Markins accessory by Kirk

If you carry your camera/lens over your shoulder attached to your tripod head; Kirk distributes a neat accessory for their own ball heads and for Markins heads.

The Ball Head Snap Collar is a simple and relatively inexpensive accessory which will take the strain of the weight of camera/lens off the ball when carrying this unit.

There are Kirk Ball Head Snap Collars to fit Markins Q3, M10 and M20 ball heads and of course to fit all Kirk heads.

http://www.kirkphoto.c​om/ballheads.html#snap​collar