I would pick template master over all the others here is why.
Excellent support, i have bought around 20-30 plugins for magento for my clients websites from the likes of gomage, aheadworks etc
but by far they are the best for assistance.
Template master have helped me with two custom development requests helping me integrate sagepay server/suite into one page.
Never once did they say no thats not included they just done it !
As i bought a few products of them they also gave me a discount too.
I wouldn’t trust the cheaper carts, these people are part time developers with day jobs, what happens 18 months down the line and we are on magento 1.7 and your cart is bust due to compatibility issues , i dont see the part time developer giving a hoot about you then.
template master offer line time upgrades, so at least your not left handing out to dry
Stick with the big developers for key components or you will get you fingers burnt.
Lastly about the price, get a grip if it helps you get 3-4 extra sales it pays for itself so why be so cheap .