REL t5i + ht1003

Hello everyone:)

I have a pair of REL t5i subs in my 2 channel system. Because of unresolved hum issues with my bridged amplifiers in mono, I have them hooked up via low input. One going into preout in integrated and one in pre out of power amplifier. (Right loudspeaker on integrated and left loudspeaker on power amp). The sub out on the integrated is free. I found a ht1003 for sale online for about half of retail. It's a bit of distance away so can't really try before buy. At the price..I'm tempted to buy it and put it in my system. I'm happy with the way the pair of t5is perform but I do love bass  and i am curious what would things sound like if I throw in Ht1003 with my pair of t5is. I assume I could just use the sub out on the integrated.  I suppose this question is for people familiar with Rels. The t5is blend very well and im Not sure if implementing the ht1003 will throw my Soundstage off and make things sound 2 sloppy. Strictly music listening:)
I had the same problem with hum. Rel recommends that you run an RCA from low input to any open rca's on the back of your preamp when running the high input. This acts as a ground. I had to do some research to find that but its straight from Rel. 
Also, many others are using several subs so I don't really see a problem.
Thanks for the response Artemus. The journey to get rid of the hum has ended and I've thrown in the towel. REL told me to give up and I've even spoken with the ceo/head engineer of the amplifiers im using. Using all methods tones down the hum(compared to just leaving it floating) but i can't get rid of it using high level.  The back and forth with REL extended just enough to let the 60 days expire. I'm a tad bitter about my experience but thats neither or there. Anywho... :)
Just curious anyone has experience using both subs for music.  
I’m running 2 REL T5s on the high input, with the neutral connectors, and resolved hum by grounding the black wires to the amp chassis 
When thinking about connecting a third sub...I just thought it was worth mentioning that the rels are hooked up to pre outs and I figured I should explain why. I didn't intend this question to be about grounding. I appreciate everyone's response in regards to grounding but I tried everything.  Read everything and watched everything.  I have emails miles long with REL and I spent 45 min on the phone with the ceo/engineer of the amplifiers I bought. He called from the UK. Only thing I haven't tried was to solder the ground wire to the outer shield of an rca plug. Rel says this will be a waste of time. I'm going to try it anyway. I dont own a soldering iron but will pick one up when I get around to it. 

Anyone use both, Rels t5i and ht1003 in their 2 channel set up? :p