8" is the most common size, so you'll get better selection in that size, but 6" will certainly work and can shave a few bucks off the cost.
Prices vary a lot. You can get a functional set in the $60-$70 range, maybe even less. You don't have to spend $300 to get a nice set. There are some $50 sets that'll cut a dado, but the less you spend, the less likely you are to get a set that performs well for a long time. If cost is the primary reason to spend less, consider using a router bit instead.
Freud is a very popular name in dado because they represent good value, good performance, and are readily available at many home centers, so you'll see it recommended often. It's worth noting that Freud makes several dado sets. For ~ $90, you can get their basic set that has 2-tooth chippers and 12-tooth outside cutters...it'll have names like SD208, Diablo, or Avanti but they're pretty much the same set...count the teeth to confirm. They also sell an excellent set with 4T chippers and 24T cutters (SD508) that'll cut cleaner, stay sharp longer, but costs close to double. Both sets are worth the asking price. They offer 6" versions of both sets...SD206 and SD506. For even more money, Freud has an expandable "Dial-a-width" set (SD608) with a similar tooth configuration to the SD508, but has an expandable hub for easy width adjustment...note that the hub requires extra room on the arbor, so it may not be possible to run the full width on all saws.
Grizzly has the DeWalt/Delta 7670 set for $90 (plus $13 s/h) that has 4T chippers and 24T cutters, excellent shim stock, and an excellent carrying case. IMHO this set represents excellent value at this price, and performs more closely to the premium sets than most sets under $100 do.
For ~ $190, the Infinity Dadonator is the simply best set I've used to date...amazing about sums it up! It has 6T chippers and 24T outside cutters.
The Oshlun sets get mainly positive comments from owners as being good value in the $60-$80 range. I haven't used either set, but their 8" set is a copy of the Systimatic 42T/6T set that I had a while back that was expensive and excellent. I do have an Oshlun 40T that I think is a heck of a bang for the buck.
The Forrest set is always very highly rated and well regarded, but is also very expensive. It's hard for me to imagine it outperforming the Dadonator, and for the prices of these things I just can't try them all to find out for myself!
CMT and Amana have good sets that are similar to each other, and similar to the design of the Dadonator except they have less teeth and cost about the same, so I see no benefit of these over the Dadonator.
Ridge Carbide is another excellent premium manufacturer who has a great set that's highly regarded, costs a lot, etc. I haven't tried, and again, would find it hard to believe it'll outperform the Dadonator.
HTH,
Good luck!
Scott Spencer
Wood Online Forum Host
Tools and Tool Buying
"I've gotta stop treating this stuff like it grows on trees"
