Worked Backwards and Would like to Hear Suggestions on Speakers

@tomic601 
Mmmm, an MBL. I haven't heard them, but I think they would be a pretty sweet loudspeaker.
@randy, 
I agree that Maggie's would be a good way to go, as well.
@OP,
I'll put in my 2 cents and give Vandersteen a plug.

The Bose were pretty sweet during the 70's-80's(another guy in my dorm had 301's that I liked alot), but technology has improved and speakers have come a long way. The closest you can get to them(901's) would be the Ohm or Shahinian- plus you would probably get better bass, as well.

 With your equipment, I think you can safely run just about any speaker out there. Though if you choose a low impedance speaker (and, maybe if you don't), you could buy a pair of Zero Transformers to help your amp.
In any case, I recommend that you try to audition as many speakers as you can. If you let us know where you reside, we can give you some dealers to contact.
Bob

HI!!

Each time I entertain upgrading an area of any system I put together, I view it as an area that should be in fact, upgraded. Not, merely a side ways step.

That said, I’d want to look into obtaining speakers that could be a better representation of the entire bandwidth and not just a portion thereof.

I’m embarrassed to say how long ago I heard the first 901s. I was summarily impressed. Back then. Since, I’ve been impressed by many more loudspeakers and have come to a conclusion of what I want from them.

As said herein, room acoustic treatments do indeed matter. However, bass is an area which usually requires the most attention. Naturally, it follows one should have speakers which reproduce that section of the bandwidth well, or have subs relegated to that job. I did not notice any mention of subs. Room size. Etc. going forward preffs as to remaining with something more akin to the 901s voice or stepping into a new world with these next choices as the Ops preffs Or intentions.

Keeping to the monitor or stand mount esthetic, well, the slections are mind boggeling. Dropping six or seven grand on a pr of monitors ought to really step up the sound, as long as the bottom octaves are not being sought in this speaker swapping out effort. Whoa.

Six grand in used monitor land is serious territory!

However, in the floor standing standard conventional vein, going used, and seeing as how power seems not in question with Mac 501s pushing things, and keeping with pre-owned units, the choices are vast.

Without preffs being named, I’d say see what you can do with a pr of Eggelston Andrea’s IIs. Everything across the bandwidth of the sound will improve. Bass. Imaging. Top end response. It would be a quite significant move up the food chain. More of a night and day affair.

Dyn Audio is another that ought to please. Its tweeter is a top notch one if it is an isotary or iteration thereof and would work well with the 501s.

Jamo is another loudspeaker I’d recommend with those amps. Like maybe the ref 800s. Sonus Faber should too. Focus Whispers could be an excellent choice if Jamos aren’t found. Former Wilson Sophia’ ii or maybe, IIIs could be another righteous option.

If panels are a serious thought, look to Martin Logans with active woofers given the power you have on tap. A more full range solution than the 3.7 Maggies.

What ever the choice, IMHO I’d stick with speakers that have an easy top end so long as the 501s are in the mix.

A good bit depends on as has been said here, the type and esthetic of the kind you seek, the room size, your own listening preffs in terms of the presentation you enjoy most, or are trying to acquire with this next speaker move.

Installing fuller range speakers will then enable your views to broaden as to what your room needs in order to allow your speakers to really blossom as you should then have far more bass than the 901s provide..

Best of luck.

No brainer - Quad 2812.  
NOTHING is as delicate, transparent, musical, realistic etc....nothing.

Mmmm, I think tomic601 wanted to refer to the German Physiks radiators.  The German Tekniks look like they'd do great at heating up the room but not with sheer spl...btu, yes... ;)
But, as with the 'small MBL', bring $....the more the better...
There's the HHR's for a 'classic' Walsh...

yes i did, thanks for taking the heat !
my thinking is if he likes the omni pattern, get an omni
the smaller mbl are an entry into this and can sometimes be had under the top of his budget
also
you could get Vandersteen 5a and turn the rear firing tweeter on !