Antminer S5 is the most cost effective miner at present. With a power draw of less than 600 watts at the wall anyone can use one at home. You would not want it in your living room or bedroom due to fan noise though.
I don't think you want them anywhere inside your house at all from how loud and hot they are.
If you are running in a area where you are worried about noise you might check out the Avalon 4.1 it's amazing on underclock how quiet it gets.
Shameless plug to new review I did on it:
https://bitcointalk.org/index.php?topic=1008726.0The S5 is also a great machine. You just you will need a spot that you are not using to put them that can keep noise away from living quarters, that's what I did with them.
I was also thinking of an sp20, I have read they are not even as loud as the S5 and out hash it.
Sp20 s not as power efficient as S5.
it is more efficient at 900gh
it is less efficient at 1300 gh
the s-5 pretty much is .50 to .53 watts a gh
the sp20 is .44 to .62 watts a gh depends on the hash settings.
Right now I am running an sp20 at 1185gh and using 599 watts on a plat psu that is 0.5054 watts a gh
I have had all three of them:
sp20
s-5
avalon 4.1
the sp20 set to 1200gh is medium loud not quiet
the s-5 set to 1200gh is nut job crazy loud without proper fan mods I can get an s-5 to do 1300gh at 55db with 35 dollars in mods.
the avalon likes to do 800 to 925 gh dead quiet decent power numbers. costly