I'm surprised nobody mentioned NAD. All NAD amps I've heard were on the warm side of neutral, and they have some good high-power power amps for around $500. For under $500 you could get a used one and if it doesn't solve your problem, resell it for little or no loss.
Perceived brightness can also be caused by a lack of power in the amp (particularly if the amp lacks current and the speakers have dips in the impedance curve at low frequencies) and the NAD power amps have current to spare.
I'm sorry you were lead astray over cables. IMHO there's far too much hype and hyperbole regarding cables. Cables can be the icing on the cake of a good system but will not rescue a fundamentally unbalanced system.
Perceived brightness can also be caused by a lack of power in the amp (particularly if the amp lacks current and the speakers have dips in the impedance curve at low frequencies) and the NAD power amps have current to spare.
I'm sorry you were lead astray over cables. IMHO there's far too much hype and hyperbole regarding cables. Cables can be the icing on the cake of a good system but will not rescue a fundamentally unbalanced system.