Help me plan my next upgrade

I'm making the jump from the Onkyo 989 receiver to separates. I just bought an Arcam AV8 here on Audiogon, and will likely close on an ATI 2007 amp this week. My 3 front speakers are M&K 150THX, the sub is M&K, and the 2 rears and 2 surrounds are in ceiling B&W speakers. I haven't yet purchased any of the cabling. The DVD play is the Denon 2900. The TV is a Toshiba 52 inch.

Where would be the biggest bang for my buck for my next upgrade?

Thanks in advance for your response.