Creeper and Sogood bring up very valid points. VMPS products tend to be capable of good bass extension but typically sound bass heavy due to the slower transient response of a passive radiator. Obviously, speaker placement is critical and i'm assuming that you've experimented in this area first. If you haven't done this, that would be the first step before you start anywhere else.
If you can't get the system to do what you want it to do after finding proper speaker placement, I would contact Brian Cheney and start looking at the tuning of the passive radiator. By changing the tuning of the drone cone via adding / removing mass, you will alter the quantity and quality of bass that you hear. It is possible that a previous owner had "fine tuned" the mass of the drone cone to better suit their personal needs / room acoustics. Since every room is different, it is possible that what worked for them sonically / acoustically may not work for you.
As to the equipment that you have, i do think that cables can make a difference and sometimes this difference can be quite noticeable. Having said that, i'm not familiar with the interconnects but the speaker cables tend to favor bass output, so those are obviously not the culprit.
As far as your CD player goes, changing tubes can / will alter the presentation and tonal balance. I would work with getting the speaker situation sorted out prior to even remotely thinking about tubes though.
Looking at your back-bone components ( preamp and amp ), i don't know the output impedance of the preamp nor the input impedance of either of them. This could come into play and might be something that you want to check into. When a component is not properly loaded, it tends to either sound overtly lean or excessively slow and murky.
As far as the amp itself goes, it should be left on at all times for best performance. Aragon's can tend to sound a tad hard & bright and slightly lean in the mid-bass ( warmth ) region if you cycle them off and on all the time. Obviously, if you can slightly soften the highs a bit ( not so much soften as "refine" ) and increase the warmth of the system, tonal balance will be slightly fuller sounding.
As far as the bass capabilities of the Aragon product line, i would stick with what you have rather than looking at a Bryston as Marakanetz suggested. The Aragon is a FAR better amp than the Bryston in terms of bass output and control. This is especially true if running at lower impedances, which if the VMPS that you have is like their other designs, probably is.
As a side note, when setting up speakers on the long wall, you tend to have a more open soundstage due to the lack of early reflections, but you also pick up some bass reinforcement from sitting in closer proximity to the rear wall. Going to a short wall placement will produce an increase in apparent high frequency content as you're now hearing a larger percentage of reflections. At the same time, you'll also lose low frequency coupling as you're probably sitting further away from the rear wall. Depending on the speaker design, one placement will work better than others. As far as personal tastes go, i normally prefer speakers on the long wall. Then again, most all of my speakers are sealed, so the added bass reinforcement that occurs in such a situation isn't as "bad" as if one were using vented ( passive radiator, ported, etc... ) designs to begin with.
Obviously, my suggestions are simply "comments" and should be taken as nothing more than a reflection of my personal tastes and observations. Others may have differing points of view. So long as you arrive at the place you want to go sonically and we ( as a group ) are able to help you do that, that is all that counts : ) Sean
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