Hi Jeff,
Don't worry so much about upgrading your machine. The Carezza is an excellent entry machine. I used one for years. The single best upgrade you can make now is a better grinder. I used to have your exact setup and after a couple of years the wear on the Solis was noticeably causing a degrade in shot quality. I ended up with a retired Mazzer, but I'd suggest looking for a Cunill Tranquilo. It's commerical quality grinder at a very low price. (used to be just under $200). Honestly, if I had bought the Mazzer first, I might not have upgraded my espresso machine yet. Once you get used to their quirks, Gaggia makes a nice machine.
BTW, I sometimes haunt the Pizzamaking forum...I make a batch of Randy's American Style crust every week. Had to start limiting my time there once I noticed that I was getting obsessive about the details...Couldn't support two obsessions... :D
Mike



