Yeah, the AMD Phenom II x6 1045T is a good CPU, but if it were me I'd wait to have enough for the AMD x8 FX8350 and the Gigabyte mobo for 78 bucks... comes in under 300 and would be a significant upgrade as opposed to something with just a little more kick.
I know how it feels, wanting to up the ante and not having quite enough, just itching to get stuck into it. When I was looking to upgrade from my AMD Phenom II x4 920, there were a number of affordable 4 core offerings available, and at the time I could have snatched an AMD Phenom II x4 955 for $107, but it wasn't enough of a jump so I waited to get the AMD Phenom II x6 1100T, which was the flagship of the range and considerably faster than the 920. It cost me $210, but IMO the performance increase justified the additional $103.
It was the same when I was looking to upgrade on that again, I could have settled for the AMD x8 FX8150 @ 3.6ghz, but given the reviews said that it was not a lot quicker than the 1100T, I wasn't too sure about going that way. However, I was offered an AMD x8 FX8170 @ 4.0ghz for 40 bucks more and I took it. It meant having to wait an extra couple of weeks but it was worth it. Now AMD never officially released the FX8170, but my supplier snaffled 2 and offered me one for being a loyal and long term customer... he kept the other for himself, as you would with something so rare.
I now have an AMD x8 FX8350 in my main rig and it is by far quicker than any other AMD CPU I've tried, and quicker than some Intel i5's and i7's according to benchmarks, so it would be worth waiting for IMHO. I know you're anxious to upgrade, and 50 bucks seems like a lot to be short of $99, not to mention $300, but I don't know that the jump to a 1045T would be that noticeable.... at the least I'd go for the 1100T, given how well it fared in benchmarks against the newer FX8150 and even some Intel offerings.
Food for thought, me old mate, food for thought.