Decent preamp

Per itsjustme's comment above:

Totally under the radar and far below your budget is the B&K Reference 30. Even though it’s a 5 channel, reviewers at the time felt that it’s 2 channel performance surpassed that of the B&K 2 channel preamp that was available at that time. Quite a thing for about $300 or less. Sold new for just under $3000. You would not be disappointed.

Just another way to look at all this. When I listen to the identical preamp you already have into a  McIntosh amp with the exact same output as your Aragon 2004 I experience a pretty extraordinary performance on all fronts with exceptional accuracy, clarity and separation. You may possibly be trying to improve the wrong end of your system. Just a thought.