Brian,
You might also look at Cloudingo (www.cloudingo.com). I took a look at DemandTools CRMFusion and Cloudingo (but not Ring Lead) and went with Cloudingo because it was browser based, had one common view/interface for de-duplication of imports and existing records, and it was cost effective.
It has some shortcomings (sophistication of boolean operations on matching expressions, no permanent memory of specific records marked as duplicate) but we've been able to work around them pretty well.
TrustRadius (our site) has a few reviews of DemandTools / CRMFusion here that you might also find helpful: (http://www.trustradius.com/products/demandtools/reviews)