Help with adding to my HTS.

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Hi, I'm wondering if you guys can help me. I'm running with:

• Yamaha RX-A1060BL 7.2 Channel Network AV Receiver
• Parasound - 2250 250-Watt THX Ultra2 Two-Channel Amplifier
• 2 Polk Audio RTI A9 Floorstanding Speaker (Cherry)
• 2 Polk Audio - RTiA 6.5" Bookshelf Speakers (Cherry)
• 1 Polk Audio - Dual 6.5" Center-Channel Speaker (Cherry)
• 1 SVS PB2000 12" 500-watt Powered Subwoofer
• Connected with Mediabridge 14 AWG-99% Oxgen Free Copper

I'm not sure if I should disconnect one of my RTI-A9s from my Parasound Amp and purchase another Parasound Amp for that disconnected speaker---so each RTI-A9 will have a dedicated amp. Do you think that will maximize the capability of my A9's?
Also do you think I should buy another SVS PB2000 to balance out the bass or get another pair of surround sound speakers: Polk Audio FXI A6---to get complete 7.1 HTS?
Any help would be appreciated...