Mike - I started with a PT175 (40hp) and was glad I did. Made a lot of mistakes in that boat, but because of the engine and design (unpainted aluminum and top speed of 25mph), I didn't hurt myself, the family, or the boat! I did go through a few props, but that was a small price. I ended up keeping and fishing out of that boat for over four years before "upgrading" to a G3 HP180 with 150hp. When I sold the PT175, it was still in great shape. The G3 with the big outboard was a very different handling ride, but my confidence in handling the PT175 (learned over five years) helped tremendously.
Of course, that was me! Some folks can start out fine with a larger boat. A lot also depends on what you want to do. If you fish tournaments regularly or your fishing is on big water, you may want an Avalanche from the get go. If you fish smaller rivers (and I include parts of the Potomac in DC) or reservoirs, the PT185 is probably more versatile. Whatever you do, look to max out the HP on the boat. You won't regret it during use or when its time for selling.