Is your Athlon quad 2.8 a Athlon II X4 630?
Have you tried overclocking your CPU yet? Others have managed to get the X4 630 to 3.2Ghz without increasing CPU voltages. AMD Athlon II X4 620 & 630
I think I'd try some overclocking before I'd slap down $160 for a 3.2Ghz Phenom II X4 955.
No I wouldn't replace an Athlon II x4 with another current quad. When you say any kind of Phenom, if you get Phenom I it's actually a downgrade, lol. Phenom II is less than 10% faster than Athlon II at the same clock, you won't see a major gain of any kind.
I've got a Phenom 9850, Athlon II 630, and Phenom II 940 by the way, all 3 systems have 4Gb DDR2 1066 memory and I honestly can't tell the performance difference in almost anything but a few applications, and the difference is small.
Oh, forgot to answer your black edition question, all that means is the multiplier is unlocked for an easier method of overclocking. It has no effect on anything except an easier overclock, and usually doesn't allow any higher overclocking if you know what your doing.
u might see some improvements in games. difference is only in the L3 cache, the athlon is basically a phenom with a little higher L2 cache but without L3 cache.
but in your case, I would not spend money on a quad phenom now, there is no point int that. the athlon x4 is a decent cpu, u can even try overclocking it a little.
diff between phenom/athlon and their Black edition versions is in the unlocked cpu multiplier. that means with the right mobo u can simply increase the cpu multiplier, giving you a nice and easy cpu overclock.