Expensive tweaks-are they worth it?

Specifically Walker Audio (High Definition Links) $300/pair and Argent Audio (Room Lenses) $400 each (3 recommended) Thank you . Yoby
I cannot speak for the Argent Room Lens, but the Walker HDI is a very worthwhile high level tweak. It should probably be added after everything else in the system is mostly correct to fully appreciate it's value.

To put price in perspective, the HDI at retail is about the same investment as a foot (or less) of the interconnect cables usually found in a high end system.

The performance is distinctly audible with my Soundlab speakers, adding impact and dynamics to the bass frequencies and smoothing the extreme high frequencies while improving depth of image. I have had others tell me that similar performance gains were had with dynamic speakers as well.
I found that the Argent Room Lenses were one of the most cost-effective and significant tweaks I have ever used. Bass performance in my room was much improved with deeper extension as well as taming a mid-bass hump. In addition, soundstaging was dramatically improved with much better delineation of individual instruments and vocalists.
I agree with Albertporter, the Walker HDLs were a definite improvement to my Maggies. I use 2 sets because they are biwired. I purchased them after hearing them on a pair of Sound Lab Ultimates. He correctly points out that your system must be 'mostly correct' to appreciate them.
The Walker HDL's do make a difference. Whether that difference is a good thing or a bad thing is purely subjective. Thing is, $300 will buy you a fat stack of records. Something to think about...
The Walkers do make a difference on my dynamic system as well, although I think they're expensive for what they are (not the improvements). The designer of my speakers did a measurement at the tweeter with the HDLs in and out of the system and there actually was a measurable smoothing of the treble output. The room lenses didn't work for me, but my system is almost an omnidirectional one, that probably has a lot to do with it; on a more conventional speaker system my result may well have been different.
I too gained a significant improvement upon using the Walker Audio HDLs on my Thiel speakers. They are very much worth the price I paid for them.
I have it about 6 months on my speakers and I forgot that it's in there. I tried to take it off one time when I was re-positioning my speakers,the result was unbearable,I did not even finish listening to one track and I have to put it back in.
It's like a lot of good things that we have and take for granted, we will never know how vital it is until we loose it.
I think expensive twerps are always worth it...oh...sorry,
you said tweaks.. Actually, some of the least expensive
are the most "worth it".
1. Make sure your cable TV feed isn't introducing DC voltage on your homes AC ground.
2. Level any mechanical source...ie: turntable, CD player
or transport.. and level the item..not the shelf they
are upon. If you don't "get" this one..try walking
uphill or downhill..and then on level ground.
3. Keep all cables as short as possible...if this is not
of merit..then why do "upgrades" of high-end gear often
talk of "a shorter signal path"... ie: more wire is
more ohm's, inductance...etc.
4. If you live in an area with decent FM stations..make
sure you have a good( if not great) tuner. There is
no better way to learn of new release or re-release
music that you may want to ad to your system..and many
towns have college stations that broadcast very good
signals and music mix.
Just some ideas on "other" tweaks....