Update - A lot happened the past few weeks. For those interested, to start with, on topic of this thread I got a Luxman 509u integrated, which I adore. This amp is clean, clear, powerful, flat, with punch while bringing out the subtlest tonalities and details of instruments across the spectrum.
Taking mainly Daveyf's advice to work on my source and front-end stuff, I started at my computer by adding Amarra software, which I find noticeably better for playback of higher-resolution files, and I upgraded my DAC to a North Star Designs USB Dac32, which I preferred on listening comparisons over the Bryston BDA-1 and new Luxman DA-200. I also replaced all my interconnects with used Cobalt stuff, and speaker wire with German 12 AWG silver wires. In addition, I put-up sound-absorbing curtains over my thin Japanese sliding plexiglass door-walls, and some foam-rubber absorbers on the reflecting wall facing me. All of these tweaks have made significant improvements, and my system sounds great now.
HOWEVERÂ…and this part might make me lose you all as friends, I finally gave-up on the Guarneris. I came to admit to myself that I am just not a small-speaker kind of guy, and much prefer a large sound that reproduces all genres of music well rather than only certain kinds of instruments. I was hit once and for all with this when I happened on a pair of minty condition Acapella Campaniles on special New Year's clearance sale, and traded-in my G's, old Luxman amp, subwoofer, plus some cash for them, in an amazingly lucky bargain.
These are definitely my sound. No more searching. The problem now is there is no room in my old Japanese house with ceilings high enough or enough room for them, so they are in storage while I look for a new house for them. I've been wanting badly to move, and this gives me greater impetus. I know I face a great deal more tweaking when I finally do find a place where I can install them, but I've learned a lot from this forum and look forward to that challenge.
In the meantime, I'm back again to my old Yamaha NS-1000X's, but now with better sources, interconnects, amp, placement, and room treatment, and the sound is all very livable until I finally find a new home for me and my Acapellas.