You can always use your starter press should you want to move up.
I went the Dillon 650 route after using a 550 for several years...but sold the 550 and any accessories that wouldn't take to the 650 to a friend for his entry...gave him a deal.
If I were going to replace the 650 today, I would have to give very strong consideration to the Hornady Lock And Load. Alf has dong a very good series of posts on his experience with it and it does appear to have several advantages over Dillon's approach to the die setup and the functioning of the powder measure.
If you want to get in at that level, check it out.
I am glad I started with a single stage press (there were no non-commercial progressives available at the time)
(a RCBS Rock Chucker Combo, it was called
http://www.midwayusa.com/viewproduct/?productnumber=646599)
because it allowed me to really learn each step in the progress, check each case between steps and see the results and understand the process.
Lyman still offers their 310 had press
http://www.lymanproducts.com/lyman/dies/lyman-310-tool.phpHere is a video of using that press and it will show you everything you need to reload...this will be only for the gun the cases came from.
http://www.youtube.com/watch?v=c_9-1oEbr9QThat is the most basic...not a whistle or bell in the whole set up.
If you want the very lowest entry level you can get, here it is
If you want to skip the manual learning experience of a single stage press, Mayer's recommendation of the Dillon 550 is a good press. If you do go progressive, and feel like jumping in at the Dillon 650/Hornady LnL level, you can't go wrong there either
There is a good book you can get to start you on your learning.
ABCs of RreloadingAmazon offers several versions of this book...one being a new copy of the one that got away from me selling on Amazon for $999.
They have a cheaper edition here. I'd guess it has all the information you need.
http://www.amazon.com/ABCs-Reloading-Definitive-Novice-Expert/dp/1440213968/ref=sr_1_1?ie=UTF8&qid=1314475805&sr=8-1Think about getting the book and reading up on reloading before you decide what you want for your setup. If the new version is as good as the one I cut my teeth upon, it will give you a good look at the benefits to be gained with the "extras".
If you do decide to go Dillon, Brian Enos has a site and he is very willing to work with you to be sure you get exactly what you need/want in your setup. I purchased my 650 through him and he saved me buying things Dillon would have included in a "cover all bases" setup. I did buy some of the stuff later when I expanded my reloading scope. I believe Alf may have contacted him when he was deciding between the Dillon and the Hornady
Good luck and I'm sure you will enjoy the endeavor.
Take care.