Originally posted by Enc0der This is very nice, but you are forgetting the fact that the K20D sucks on AF and general performance.
You missed the whole point. The point is that it DOES NOT SUCK when you make a reasonably comparison. The point is you are comparing apples to oranges. The point is you are comparing the speed of budget screw lens to a high performance very expensive USM lens and saying the body is responsible for the difference and asking if the next body will be faster. It's not. The L glass motor is faster and quieter, on Pentax, that's equivalent to the SDM lenses. The body has nothing to do with it.
If you're unhappy, change. Sell your K20D and lenses here on the marketplace and I'm sure people will treat you very nicely and give you more competitive prices than you'd get on Ebay, even though it's probably the people here that'd also be the ones buying it from you there as well.
Your reasoning, however, is absolute crap.
What I'm telling you is that you will waste your money if you buy a K-7, put that Tamron lens on it, and expect it to behave as quietly and quickly as your friends camera. It may have a TON of other features and advantages you'll like, but a budget screw lens will not behave like a top of the line USM or SDM or HSM lens, and if that's your only criteria, you're going to be unhappy.
In even smaller words, without the numbers, since they confused you:
You should not buy a K-7, put the same Tamron lens on it, and compare to the 50D and L glass. You are better off spending money on DA* glass and swapping lenses, or a spare body, and get more versatility for the same cost as that L glass OR swapping systems and borrowing your friend's lens. You can't just look at the numbers on a lens to compare them, you have to know what the letters mean, as well.