sub/amp/speaker hookup

[rebith75]

forgive me if this post frustrates you, trust me I have done countless research but still wondering about some basics...
I have 4 bookshelf speakers (diyish dayton br-1's) and a cheapish denon 2channel amp

I am looking to build a sub using the dayton quatro 10's

now for some basic questions:
what is the best way to set this all up w/o getting a new receiver with a sub output seperate? Looking at some plate amps I see a high level and low level in/out, the low level is rca and high level is speaker wire, would I just take speaker wire from the L and R outputs on the receiver to the high level inputs on the plate amp then output that to the bookshelves? Does the plate amp do the crossing over?

Is 100W (dayton SA70 or Dayton SA100) good enough for the dayton 10" quatro, when going from a cheapish receiver first then to 4 bookshelves?

Thanks for your help

[rebith75]

also could I just get rid of the old receiver and invest in a bigger plate amp around 250-350, take the rca cables from my dac into the plate amp then out to the speakers??? would this work? would it be better?