There are three elements about your system that you have not mentioned. One of course is the room, and you could look to treat it. The second is power cables - yes, they can make a big difference and whether they can make a bigger difference than re-wiring a dedicated link depends on how bad the existing one is, but the important difference between the two options is that you can try the power cables at no cost first to see whether they are worth it. The third issue is vibration control ie. the physical interface between components/cables and the room. The area of vibration is tricky and where the final tuning takes place (IMHO) but certainly requires attention if you have not done so already. A high-resolution system is not really possible if there is a weak link in the chain, and the chain includes; a relaxed listener, low ambient noise, the room, speaker/listener positioning, clean power, final conditioning via good power cords, the components, the interconnecting cables, clean contacts and vibration control. Until you have addressed all of these to an adequate standard then equipment upgrades and tweaks such as Black Gates will not be very cost-effective. Living in another country, I do not have direct experience with all of your equipment, but have some comments. Despite all the reviews of the DH Labs interconnect, I believe you will get a big improvement in resolution from upgrading it. I had some and would describe it as doing the least damage of any cable at its price because its errors are more ones of ommission than commission. But there are far more resolving cables around for a little more money - but they are of course a two-edged sword in that they also reveal problems with your source. I would strongly recommend you try some other cables on a loan basis. Try Fatwyre.com as few dealers are in a position to loan you a range of cables that have been run in. My other comment is regarding the 20 feet of speaker cable. IMHO speaker cable is so important, and the degradation can be very marked with lengths over 2 metres. A second-hand long pair of JPS Superconductor might fit into your budget, and allow you to place your amplifier closer to your speakers. The issue to watch with this is you may lose the benefit of star-earthing your system if it means your amp is on a different circuit from your other equipment.
Fine tuning: advice?
I have a system that gives me the musical satisfaction I have been looking for for almost 40 years, but, like all of you, I'm looking for those tiny improvements that make a great system greater. I have about $300 burning a whole in my pocket and I'm looking to get the best bang for my buck. I am considering three specific approaches. One:going to a biwire set of LAT SS800 silver clad speaker cables. Two:replacing all 16 electrolytic capacitors in my preamp with Black Gates. Three:installing a dedicated circuit for my system outlets. My system as it is now:Legacy Classic speakers; Bryston 4BST amp;AMC 1030 tubed preamp with EI and Sovtek tubes;Assemblage DAC 2 with upgrades;Audio Alchemy DTI Pro;Rotel RDD-980 transport;DH labs BL1 interconnects;WireWorld Royal Starlight silver digital interconnects;Tara RSC Prime 500 speaker cables (20'lengths-single run).Thanks for any advice.