I have the Delta unit for about 4 years and it will go 4". As for surfacing
"thick" stock - It is VERY useful and the extra capacity is good. I will
sand the edges of a set of boards by clamping them together, "standing up"
and running them through. The drum sander is a great way to get a WHOLE
bunch of parts exactly the same thickness or width. Would I buy it again?
Hope this helps - however if your needs are on the smaller side I think
Performax just came out with a bench top unit that will sand ~6" wide.
My only reservation with the Delta unit is that you really can't take off
very much material in a single pass - I wouldn't even go 1/16" as it'll
stall out. I accept this as one of the machine's limitations and don't rely
on it as an abraisive planer. On the plus side, it's a godsend for sanding
chair parts - dozens at time, and QUICKLY...