Not much doubt that the S1500 is a solid value. I think a better money comparison is the Ultra vs the S3000i. I own the S3000i (which is also less money than the SVS) and SB13-Ultra. The Ultra I use for music only, while the S3000i is mainly for movies and TV. Both do their jobs exceedingly well. I slightly prefer the Ultra for music (the S3000i is still very good) and prefer the S3000i for movies (more tactile feel).
The Ultra's amp has several important features. Since I use it in a 2.1 setup (no bass management), the Ultra comes with different octave slope adjustments on its high & low pass filters in order to fine tune the crossover, and a couple other handy implementations (the two PEQ's already mentioned and room gain compensation with adjustable slope, etc).
Music area: Magnepan 3.6, McIntosh MC2205 amp & C48 preamp, SVS SB13-Ultra, Oppo BDP 95, dbx 3BX, and assorted equipment.
Movie area: EMP Tek E5Bi (were rebadged to R5Bi), RBH/EMP Tek R55Ti, PSA S3000i, Denon X2000, Oppo BDP 83.