How deep should I plant DAHLIA'S & what about spacing THEM??

Question:I may have to re-dig/plant, as I planting them down in about 5.5-6 inches into soil & only about a foot spacing of 4 tuber [clumps] just now .. should i replant them deeper,ect?
Noticed there's just a tad slight bit of clay in mostly top soil the area where I planted the dahlia's
Does it require a bit more SAND do you think?
ANd how many flowers should one estimate that each CLUMP would produce when mature in growth please?
thanks!

Answers:
A couple of good reference sites can be found at:

http://www.dahliabarn.com/care.html... and

http://www.dahlias.com/index.asp?pageact...

*~Enjoy~*