The answer to your question is going to have quite a bit to do with what you are personally into. I have had over 15 different prosumer and commercial espresso machines in the last 4 years, and my answer would probably be much different then the answers of the majority of the individuals in this forum. After experiencing many espresso machine, all prosumer / commercial semi-auto or manual or spring lever, I can tell you the the old school commercial spring levers pull the best shots time after time after time, for my palate anyway. Now, whether you are an individual that would appreciate, and be patient enough, to learn how to master a lever is another question. It definitely takes a certain kind of person, and there is nothing wrong with people who love and stand by their prosumer semi-autos. The two types of machines are very different and both have their plus sides. From my experience though, the results are not even in the same boat. They are incredibly different, and it really depends on what you are looking for in the end cup that will dictate what will ultimately make you more happy.
Either way you go, I would strongly recommend that you go used if you are handy at all. The money you will save / have to spend on other coffee accessories will more than be worth the patients it takes to procure a machine retailing for $2,000 plus for under $800. If you do want a prosumer semi-auto I agree with a lot of the above advice. You really cannot go wrong with a Vibiemme Double Domo with a pid, Alex Duetto II, Alex II or Vivaldi II. The Vivaldi II, Alex Duetto II and Alex II will all have rotary pumps, which is a big plus.
Personally if I were going to buy another machine right now, I would go with the late 70s Brasilia Single Group Commercial Lever on craigslist San Fran,
http://sfbay.craigslist.org/eby/for/1762141670.html. The seller is asking $1,250, but you could probably get away with $1,000. If you do not live in the San Fran Area shipping would add another $100-$150 with FedEx ground. As long as the person did a decent job restoring it the espresso machine will outlive you, and I cannot say the same for any of the above mentioned semi-autos. To me more parts equal more problems. Lever espresso machines only have 2 electronic parts, a heating element and a pressure stat, and 4 if you want to add a PID and brain.