I had my Shanling CDT 100 modded with good results. I agree with much that has been said
1. It needs to be a keeper, don't expect to get your money back on resale
2. Look at feedback on the various companies
3. Start with what is a top, recommended unit in the first place.
4. Try and audition first, even better, compare a modded and unmodded unit, but thats hard in practice.
5. Speak to the modder, does he seem a straight shooter.
My next step, a Great Northern sound Co modded Resolutio Audio opus 21., when I can get the cash together.