using an old receiver with active monitors to get better low frequency response

I have an old 2002 koss 5.1 receiver lying around my apartment not getting any use along with the sub that came with it. I currently use Swans D1080MKII's on my computer for listening to music, and watching the occasional show/ playing a few games when i get the time, but the koss receiver has one RCA output and I was wondering if i run the audio from my computer (which just uses the ALC889A audio codec) to the receiver and hook up the old sub and plug the d1080's into the receiver, would i experience improved sound quality? I cant seem to find any information on how low the sub will go frequency wise but here is a link to the old system i have: http://www.amazon.com/Koss-C220-Rece.../dp/B0000632G2

I plan on upgrading to "real" receiver and sub soon, but i plan on continuing to use the d1080's for a time with the receiver (and sub) until i can afford the passive speakers i want to get. Is it worth it to get the receiver and sub now and use them with the d1080's or is it better to just wait and get everything in one go?

I would do a setup and see what kind of sound can be had
my old Carver Tfm 55x and 901 Bose along with an SVS 12 ultra/2 sound nice fed thru the Asus DX2
Dolby Pro logic 2x and a flat EQ curve makes everything from movies to all styles of music a sonic treat with no adjustment needed