Are your surround speakers direct radiating design or bipole or dipole design? You aren't supposed to be able to tell where the surround speakers are located - that is the ideal - so I'm not sure what else to ask.
Have you tried just connecting them to the front L/R outputs of your amp and seeing if they sound strange? Do you get a nice full range sound down to the mid-bass or do they sound thin? Could be out of phase. Also try with bass heavy music playing one side at a time with the balance knob - do you get more bass when only one speaker is playing?
2-Ch (HT L/R): Oppo BDP-105 BD, Adcom GFP-750 pre, Bryston 10B Sub Xover, Bryston 4BSST2 / Paradigm Signature S4 v.2 (L/R), (2) SVS SB12-NSD (Subs)
Home Theater: Bryston 4BSST2 amp / Paradigm CC-590 (C), Outlaw 7700 amp / (4) Def Tech UIW-RSSII (LS/RS/LB/RB), Samsung 46” 3D LCD