You have noticed an improvement so far, therefore, I suspect you will ultimately be happy with your ARC. With my ARC I found the stock Sovtek tubes to be a bit bright and the bass to be OK but not great with my B&W Nautilus 805's and dual Velodyne subwoofers. I replaced the coupling capacitors with Infinicaps which are the caps ARC now uses in their new units. I switched to Seimans NOS tubes and bought a set of tube rings from ARC. The improvement is vast. The highs are extended but non-agressive. The mids and upper-mids are much more open and airy and the bass a tad more powerful and much more detailed. Less fatiguing.
If you aren't a big tweaker and don't want to venture into replacing the capacitors, you may want to try the NOS tubes and tube rings. Big improvement. I also found that with the tube rings that you can do a bit of tuning by adjusting how far up or down the tube you place the rings. The higher up the tube they are placed, the less affect they have.
Enjoy. Woodrow
If you aren't a big tweaker and don't want to venture into replacing the capacitors, you may want to try the NOS tubes and tube rings. Big improvement. I also found that with the tube rings that you can do a bit of tuning by adjusting how far up or down the tube you place the rings. The higher up the tube they are placed, the less affect they have.
Enjoy. Woodrow