The MA 500s are mono blocks and you can NOT bridge mono blocks. If you try you will blow them instantly and they will be boat anchors.
Next The RTi12s are rated 8 ohm by the manufacturer but they are four ohm as you can surmise from the driver layout. In fact their impedance drops below four ohms and they are a difficult load.
Manufacturers generally are dishonest about impedance ratings and take an average of the impedance curve, which is bogus and means nothing.
A general rule of thumb is actually minimal impedance plus 10%, which put yours actually a little below four ohms.
I managed to download a manual for that amp from Hi-Fi engine. There is an interconnect for bridging. However impedance is 8 to 16 ohm. That rules out using bridged amps with your speakers.
I have no phase curve with impedance for those speakers, but it has a passive crossover in the 100 Hz range, never a good idea. I would suspect the phase angles are highly adverse, that usually goes along with that approach, as well as many other ills. So I would bet that at some frequencies those speakers look close to a short circuit at some frequencies.
Bridging is something I never recommend unless you have good service gear.
Each amp is responsible for just +ve defelctions or just -ve deflections.
You really have to tweak amps with test gear and make sure their gain structure is identical. Small errors in gain result in very unpleasant crossover distortion.
So apart from the low impedance intolerance which leads to amps blowing in bridged format, there are a lot of other disadvantages, especially related to the fact that the amps are seldom exactly identical, which they have to be as a bridged pair.
There is far too much nonsense and enthusiasm around bridging.
My advice is always, if you need more power buy bigger amps. That is a much better solution.
