Mixing REL subs, great idea or terrible idea?

Short version:  Anyone have experience mixing and matching REL subs (T, S, R, etc...)?  If so, do you have any recommendations/warnings?  
Long version:  I have recently been integrating subs into my system (MacBook Pro > Allo USBridge signature > RME-ADI2 > Musical Fidelity A1008 hybrid integrated > Spatial Audio M4 turbo S) and have decided to use Rel subs for their musicality. I currently have a T7i parked in one corner but want to level out the room with another sub in the adjacent corner along the front wall. I love the T7i but keep coming across the occasional S/2 at a screaming deal but hesitate to buy as I’m not sure it will intégrate well with the T series (class AB amp on the T’s vs Class D, different chassis material, etc...). Not sure if these differences on paper would translate to any audible differences.  This is all further complicated by the sub needing to be white (for the WAF), and me being thrifty and only buying used (for the retirement). Anyone have any experience with this?  Bear in mind this will all be calibrated through DSP once the room is fully set up. The last sub and a new couch are the last items I am waiting on before starting room treatment and DSP. Thanks for chiming in!  Apologies as I am a noob at this.