Some times stability is hindered by unstable power. There is no doubt that the Antec PSU is better then the a-Power. So there is a good possibility you will be able to stabilize your OC better. But there is no guarantee it will work. There may be several other factors regarding your OC limitations.
Now i use to have a Hiper Type-R 580W PSU on my system and was limited to 2.8Ghz on my Opti 165. After i got my Corsair VX550 i was able to push it up to 2.9GHz. So power can be one of the many limiting factors.