Hi Pelo,
If you have the budget, then go for XA60.5 (but I'm pretty sure XA30.5 is enough for your 93db 8ohm speakers). You cannot go wrong with Pass XA.5 series.
No, if you have a DAC with volume control, you don't need a pre (using a pre is YMMV. I personally prefer with a pre). But you should look for a DAC with analog volume control instead of a digital one.
NAD M51 DAC ($2k) is a good choice.
If $$ not a concern, this is what I'd like for your system.
1038 Be speakers
Pass XA60.5 amp
Pass XP-10 pre
Audio Research DAC8 (or NAD M51)
Empirical Audio Off-ramp USB to coaxial converter (reclocker/ de-jitterer)
Mac Mini with flash drive and power supply upgrade (Amarra or Pure Music software)
Grover Huffman ICs, digital cable, speaker cables and power cords