Tenny, welcome. In general the advantage that a vertically oriented speaker has over a horizontal MTM arrangement is a wider and smoother horizontal dispersion of sound. The VP150 has a unique TMMMT arrangement which is said to be significantly better than an MTM in this respect. The advantage of using dual verticals, either directly at the side of the screen or directly at the top and bottom edges, is that this arrangement makes the center channel sound appear to come from the middle of the screen.
No special receiver is necessary; the two speakers are simply connected in parallel to the center channel output terminals of an HT receiver. This parallel connection results in cutting the impedance of the center speakers in half, compared to their usual impedance. This possibly could result in excessive current being required at some extremely high sound level and the protective circuits shutting the receiver off. In most cases, however, this problem doesn't occur and shouldn't be assumed.
Incidentally, if when you speak of "completing" your 5.1 system you mean that you don't have surround speakers either at this point, it's strongly recommended that you add QSs before the center speaker if the budget won't handle both at this time.
