The DV series and the 8600 are two different animals. The DV series are oriented more for VHF and UHF digital work, and not quite as good on HF, IMHO of course and as always, YMMV. The 8600 is more of an HF workhouse, with some digital modes available on VHF and UHF.
They also have a completely different "feel" to the way that they handle in actual operation across the bands. I'm fortunate to have both, but I would strongly suggest that if this is going to be a major investment, you get at least 30 minutes of "hands-on" with both radios before purchasing.