Audiolab CDT6000 Transport and the Musical Fidelity V-90 DAC is a nice combo. You'll spend about $500 for transport (Audio Advisory price for new) You can buy a very good digital cable for less than $250. Audio Art, Straightwire, Acoustic Zen. So many to choose from. I won't name the other 100+ of them. I just own at least the 3 mentioned. Used usually comes with burn in time served, also. :)
Pre+ Amp combo is a definite. Adcom 555 puts out 320/4 0hm load.You can buy a good 555 for $350 to $500. I have 2 555s and will run them in mono once in a while. ( Claim 800+ watts into 4 ohm. I also use them on my Acoustat Spectra 3s in various configurations. (One amp, bi-amp, 2 amps using the internal crossover)
The 3.7s are just fine with me. I have had the Acoustats since 1988. I think the Maggies will take me down the road until the 6 feet under pair come out.