Well, it is possible to wire two speakers in parallel off of one amp, but it puts an extra burden on the amp. There are actually instructions for doing this in the Model 1050's manual (it was a 6.1 receiver, but they offered a way to drive two surround back speakers off the single surround back amp channel). Here's what that manual suggests:
There are two easy ways to wire the speakers in parallel. One is to run wires for each speaker directly back to the output terminals on teh receiver so that both are connected directly to the center surround output. The other is to make a direct run from the amplifier to one of the speakers. Then connect wires from the positive (red) terminal on that speaker to the matching terminal on the other and from the negative (black) terminal to its mate on the second speaker. Because running two speakers in parallel will halve the impedance seen by the amplifier channel driving them, you will need to set the Impedance Selector on the back panel to 4 ohms.
In the case of the 7700, there's no impedance selector to worry about - it will handle the 4 ohm load just fine. If you had a pair of low-impedance, low-efficiency speakers, you might want to grab a M2200 to drive one of them and split the pre-amp output, but the VP-150's are rated at 6 ohms and 91dB efficient so they'd probably be just fine.
From a practical standpoint, I agree with Doug that a single center is probably best if you can place it well. The VP150 is a pretty substantial center channel - can you move it to on top of the TV, or are there space restrictions there as well? If you haven't done so already, you might try aiming the center up toward the listening position. I've had to move my center off of the top of my TV (it's more than a foot above the top of the screen), and by aiming it down toward the listening position I've been able to get pretty satisfying results.