Passive subwoofer...huh???

Ok, I am a dufus. I just bought an RBH VDS-10A passive subwoofer on eBay. I have a decent system; Threshold Forte Model 3A amp (200 wpc into 8 ohms); KEF Reference 103/4 loudspeakers; Parasound PLD-1100 preamp & Arcam Alpha 8SE CD player. Sounds fantastic, with the KEFs just a tad weak in the bass department. Didn't want a powered sub (too much like home theater, I thought), so I saw the RBH passive sub with its nifty 10" aluminum cone driver and said "Eureka." Naturally I bought it. No thinking, just bought it. Then it occurred to me; can I power it directly from my amp, or do I need a dedicated subwoofer amp??? If I drive it directly from my amp, should I run right and left channels into it (it only has one set of 5-way binding posts on the rear), or should I just run one channel?? Have I totally wasted my money?? I'm assuming the sub has an internal "crossover" to limit high frequency input, but I don't know that either. Doh!!! Help guys. -David (should be "KefKing" & not "Klipschking")
You have to power it from the speaker outputs on your amp. You will probably need to go into the sub and out to the KEFs. It would be best to get an outboard amp though. It will not be as good as a powered sub. At least I don't think so.
You may need an outboard sub and an outboard crossover - inother words, all the things that go into making a powered sub. If you need a good outboard crossover cheap, I would recommend the Behringer 2496 line - great sound for under $300, available from Guitar Cneter or online at Musician's friend.
Try disconnecting one fo your main speakers temporarily and connecting the sub in its place to see what kind of sound you get out of it. If it has an internal crossover, you should only get very deep bass notes; vocals should be unintelligible. GOod luck.
I prefer the Reckhorn A-401 from DIY HiFi Supply to the Parts Express unit. I own both.
Google 'plate amp' and have fun with your new DIY project!
The Reckhorn amp/crossover is a good suggestion, here is more info on it.

If your preamp lacks a second set of line outputs you'll have to get RCA splitter adapters. I know Vampire makes them - just a gold plated brass piece w/ one male RCA and two female ends.
NHT makes a couple of nice little sub amps that are stand-alone units with adjustable volume, crossover etc. which would make your connections really easy. Try Ebay if not here on Agon
I also recommend the Reckhorn A-401 amplifier for your subwoofer. An excellent amp with many adjustments for fine-tuning. Details at
Specs from their site:

System Type: Non-powered Subwoofer
Frequency Response: 30Hz-200Hz (±3dB)
Sensitivity: 87dB (2.83V @ 1 Meter)
Recommended Power: 100 - 200 Watts
Drive Units: (1) 10" (254mm) Aluminum Cone Subwoofer
Crossover Frequency: N/A
Crossover: N/A
Impedance: 4 Ohms
Cabinet Material: Medium Density Fiberboard (MDF)
Cabinet Finish: Black Oak Woodgrain
Dimensions: 14-3/4" H x 14" W x 16-1/4" D
(375mm H x 356mm W x 413mm D)
Weight: 38lbs (17.24kg)
Warranty: 5 years

You need a crossover and might as well get a separate amp.
Thanks all! I have taken your advice and I'm looking at either a Reckhorn or an NHT dedicated subwoofer amp... should be pretty tight when I'm done.