A DAC to beat NAD C541i?

I've had NAD for about 6 years. It used to be a good one 6 years ago in my system, but now I think it is a bottle neck in my current system -- Tyler Taylo 7U, Linn AV5105 amp, Rogue Magnum 99 preamp.
My friend brought his Rega Apollo CD player and compared it with my NAD on my system, but I did not hear much difference, except Apollo sound a little bit more warm. But I liked NAD's more bright sound.
If Apollo is a real good one at $1000, I guess I need to spend over $2000 for a new CDP to for better sound.
Instead, if I want to go for DAC with NAD, which DAC (at $500~1000) would be best to beat both Apollo and NAD?
Which CD player (used at $500~1000) would be far better than Apollo or NAD?
Thx