Underpowered?

Before you change equipment I too strongly recommend playing with speaker placement AND listening position. I too had this exact same issue when I got my floorstanders (Spendor D7.2) and thought a sub could fix it, it didn’t sound ‘better’, I could just hear an exaggerated boomy bass that was separate to the speakers. So I spent hours moving the speakers around and at the same time moving my listening position around. What you might have is a null where you are sat which is cancelling out the bass. If you find standing in different places gives you more bass, then there is bass in your setup, you just need to find the listening position coupled with speaker placement that is the bass sweet spot. I have the Hegel H390 and personally love it, the bass it produces has a wonderful tone that is addictive. I am not suggesting it is THE amp or that it will improve things, just that I’m a happy owner of one of the amps you mentioned.

Room treatments will help the bass response further but just make sure if you are going to use them you get something that will actually make a difference. For the lower frequencies it is all about the depth of the trap, thin traps will do nothing to slow down the lower frequency waves which can be cancelling each other out.

Finally once I had found my preferred speaker and listening position, I purchased a basic app called HouseCurve and that was a super cheap way to get some feedback on the in room frequency response. This app is in no way professional like REW, however it did give me the frequency ranges that I had bass dip in which I then boosted with parametric EQ and reduced slightly the upper frequency peaks. Together that massively balanced out the sound bringing the bass through even more. If the highs are dominant you’ll notice them more and reducing them slightly can bring through more bass perception.

My big takeaway is there is a lot you can do, which really is the fun of owning a system, the tweaking and trialing things. Simply replacing the amp may not bring any improvements if it’s actually the room and placement of speakers and seat that are the issue. Try all of the above first and if there are no improvements then you may need to upgrade. I’m from the UK and we tend to try and not run subs, your floorstanders will have enough bass and it is better (imo) to get it out of them rather than just over-boosting the bass with subs that aren’t integrated properly. I now don’t use a sub for music as my setup has it all following the work I carried out above, the sub only gets turned on for films and at this point only provides rumble.

@dridel Congratulations on your new speakers! 

I grappled with a similar problem over the past three years. Having moved to a new house my B&W801M S2s didn't sound the way they used to. I upgraded the XOs, then the preamp. Had my Krell KSA-250 recapped. All to no avail: the bottom octave was still AWOL. Then I had a lightbulb moment: maybe the problem was the room. I lugged one of my BK subs downstairs and hooked it up. Result! The bass was back.

Ordered two new subs and dialled them in. Now the system sounds better than it ever has.

I reckon your room doesn't play nice with the new 702s. They aren't speakers that are hugely difficult to drive, I don't think your MA252 is the problem and a new amp is not going to fix things. If changing the 702s' room placement doesn't improve their bass response and apart from that you like they way they sound, the quickest, easiest, and most satisfying way to address that issue would be to install two subs. Been there, done that...

REL (and BK) subs feature a high level connection which I prefer for a two channel connection. You do not hear my subs, you only feel their "foundation", along with a wider, deeper sound stage. A friend who popped in for a listen didn't even notice them sitting in the background as the music was playing...

Good luck!

Adding subs will be my number one ☝️ choice or buy Class D amp to bi-amp

Class D for lows and McIntosh for highs 

Tricky situation and logical way out not always a help. If you was satisfied with your three way sound signature adding subs could not be solution. I would go with amp or speakers replacement. 

The first thing to do is if you have standard wires, you will need a jumper if there is 4 posts and you have 2 wires to connect( plus and minus)

Second, play some music walk around the room.  Do you hear boomy bass in some places and none in others.  Go to the corners, is it boomy there?  If you hear this then you should try moving your speakers around.  I point them right at me and sit back the same distance as the speakers sit apart.  Some speakers only need to be tilted in slightly.

Third, even if the room is not too bad for acoustics, a sub is a real helper here.  Very few speakers go down low enough  in the bass.  Especially, since you said you liked bass.  But you may find once you fix positioning and room problems your speakers are OK.  Try sitting a sub right beside a speaker.  Point it toward you or the wall.  If you have a second sub put it along the wall by you. 

Fourth, you are used to the B&W sound so I would not ditch these speakers...yet.  Same with the amp.  Depends on how loud you like your music.  But amp replacement is after you try a sub.  A powered sub has it's own amp and bass takes the most power, so your 252 may be enough.  Also, less excusion of the woofers reduces distortion of midrange frequencies.

Don't feel bad, they always say build your system around your speakers.  :)