In a perfect world there would be nothing but XLR. 100% of noise issues, be it RFI, EMI or ground loops, can be traced to the use of unbalanced connections. The pro-audio world recognized that circa 1970, adopting a clean sheet of paper philosophy that within a very short time frame virtually eliminated the use of unbalanced connections, starting with the microphones, extending through the signal chain to the power amps. If consumer audio had done the same there would be no "I've got hum" threads.
I wonder why they didn't? Cost?
I think the op recognizes that 2 10's in a 2 cube sealed box aren't going to be as good as a massive 15" or 18" Subwoofer. The bigger issue here is there seems to be more more output coming from an 8" 60 watt ported sub than the sealed 10's.
I've modeled an 8 inch infinity with 60 watts in 1 cu ft and 2 cu ft ported boxes and while it was possible to surpass the output of the sealed 10's 2 cu ft, (the 10's had 300 watts before excursion) it only happened at 50hz by a db or 2 with a high tune and very peaky response.
Granted that was an 8 inch car sub so grain of salt, perhaps the op's 60w 8 inch is more effecient and has noticeably more output at 50 hz than the Infinity Beta 8 i modeled.
Still those 2 10's should be kicking the crap out of that ported 8" below 40hz.
Edit: It actually looks like the 8" ported could get near the performance at 40 hz as well in a 1.5 ft box but thats with a 5db peak and it's down 10db from the sealed at 30hz and a hipass filter lowers the 8's by a couple db as well.Edited by Mik James - 4/23/13 at 10:50am