Hi Ken
Welcome to the group...I think you did the right thing by going for speakers to grow with...using a MAC as source is not uncommon and can be made great...I assume your files are lossless and therefore all you would need is a DAC to take the information and translate the digital signal to analog in a quality manor. Look at Benchmark's DAC1 for around $1k. Also, a used integrated of good quality would work...I'd wait to get a little more dough together in order to do your speakers justice.
Just some thoughts...