I recently decided to step up from my turret press into a progressive setup, and so faced the same quandary as you. I asked around and scoured the web looking for comparisons, and found them...lots of them.
I will post the URL to the best comparison I was able to find on three popular reloaders. I didn't write this article, but I certainly appreciate all the great points he makes concerning the Dillion 650, Hornady Lock N Load, and Lee Autoloader.
After doing a lot of research, I ended up going with the Hornady Lock N Load AP press. And so far, I haven't been sorry. It's a great press, and doesn't cost as much for caliber conversion compared to the Dillion, according to the numbers I could put together.
Bottom line is the Hornady and Dillion are both great presses, and except for the money there is not much difference in them. And as far as the powder check goes, I have one on my Hornady. It is the Hornady Powder Cop Die, RCBS also offers a lock out die for this.
Good luck with your decision.
http://www.comrace.ca/cmfiles/dillon...Comparison.pdf