Budget Strategies forTightening up Bass?

OK... I did move the speakers; I didn't have alot of room to play with, but now, at a distance of 30" from the wall, rather than 10", the bass is much more defined. In fact, it sounds pretty darned good on well-recorded cds. The sounds-stage is deeper and imaging is better. Could it be better? Probably, but I don't have the luxury of a dedicated listening room. I contacted silverline and Alan Yun asserted the speakers are "desiged to be ported" and that plugging the ports "could damage the woofers". Perhaps this is his standard fine-print disclaimer and does not so much represent an actual risk, but even so, I'm not inclined to start stuffing anything into the 17.5's. For me, they were an expensive purchase. I'm still going to try what others have suggested, in addition to speaker placement.I don't think it has to be a black and white, "this" or "that" approach.

Plugging the ports will reduce the excursion-limited power handling above and around the tuning frequency, and increase it below (where it falls rapidly with a vented design). You're not pushing them with a big amp to begin with so I think you would be fine. However re-positioning speakers and/or listening position is the preferred approach; I had been under the impression that wasn't feasible in your situation, and am glad that you were able to try it.

Duke

DYI room treatment - bass traps in the corners and absorption at the 1st reflection points. You will be amazed by the results.

I have these speakers and not only do they put out tremendous bass, but also clean and fast bass. They are powered by the Rogue Audio Cronus tube amp and the combo sounds magical with the VPI Classic and Lyra Delos cart. I don't agree with opinions these speakers are not tube-friendly. I do agree, however, that impedance matching can help. I believe the nominal impedance of the SR 17.5s is 8 Ohms and switching from the 4 Ohms to the 8 Ohms taps resulted in fuller and heftier bass.

As a few wise responses suggested, the positioning of the SRs is critical. You had them way too close to the walls initially. I'd suggest at least 2 feet from the side wall and 3 feet from the front wall. I faced a big challenge in my set-up as my room is roughly 12'x11' and I knew taming the bass was going to be a problem. In addition to placing the speakers as far from the walls as I could while maintaining the imaging and the soundstage I preferred, I also treated the room with some dyi fiberglass panels. I bought a box of Owens Corning series 700 2'x4' fiberglass boards from a local insulation materials shop. Ten boards cost me $140. If you have a big supplier in your area, you can get them as cheap as $83. I then bought 2'x4' sheets of particle board from Home Depot and some fabric from a fabric store. It took me about 30 minutes with the help of my girlfriend and a staple gun to make several acoustic panels. I made a few with 2 fg boards per panel to make them more effective in absorbing bass. Considering the size of the room, unavoidable proximity of the listening position to the back wall and the amount of bass these monitors produce, the sound is superb. Speaker placement and room acoustics simply cannot be overstated.

Based on the impedance curve of the Prelude http://www.stereophile.com/content/silverline-audio-technology-prelude-loudspeaker-measurements, Silverline may not be the best match for a tube amp.

Oh, really? Here's a direct quote from the manual:

About Power Amplifier

The standard impedance of all Silverline Audio speakers is 8 ohms. Their exceptionally stable impedance loading favors single ended tube amplifiers, as well as low powered solid state amplifiers.

Care to retract your statement?