All I can say is if you liked Supersprint sound then you'll like the Evolve Race too, since it is indeed Supersprint Race for 1M made for Evolve UK. It fits every criteria you mention and you shouldn't have any problems to import it from UK to US. I imported it easily to Chile after all but ended up paying quite an amount of taxes due to tax system here, should be much less for US. Evolve gets great transport quotes as well as an amazing price for the exhaust, it arrives in just a few days to destination. You better mate it with either Maddad or N55 but if you are not after too loud then you'll probably be safer to go with N55 like I did or maybe with stock mids even. Read my relevant threads about the details and believe me it just gets better and better. In short, it gets loud, really barking, deep and sporty noise when you kick the gas and pass over 4000 rpm, below 3500 to 4000 or if you are gentle with the throttle it is really not too loud, a loveable double personality I would say. It is deeper and burbling at all rpms, with minimal drone compared to stock and noticeably better response and high rpm revving, just zings to limiter. Fits like a glove with zero issues as well. Quality seems without any issues but don't expect a visual vow element like an Akra. I guess for half or 1/3 of Akra price you could easily live with that, it looks much better than stock and muffler itself is much smaller and less visible from outside too. I got respectable increase in whp and wtq as well without any tune.
You can stay relatively quiet with it in city driving if you want to, but cold starts are louder than stock. Stock was not bad at all at cold start too.
I didn't experience any downsides of this set up yet, it is my favourite mod together with PSS set, they totally transformed a very good car into a great one.
One problem: I don't know if any left for sale from Evolve, better contact with Imran or somebody else from Evolve and don't be shy to ask initial group buy price if you are interested. It took me almost a year to buy one and now I am feeling what was I thinking!
The other alternatives you mention I don't have any first hand experience so I can not comment but they all sound good from videos.
Among all 1M exhausts my favourites are the one that I chose of course, plus Meisterschaft and Lightweight Titanauspufflangen. I like the Akra sound in general too but only if it comes with dps and if I wouldn't pay it myself
"The mark of a great car is one whose overall competence exceeds what you should expect from its individual components and the 1M does just that", Chris Harris.
BMW 1M-SOLD-: TECH: Evolve Race+N55mids, Evolve IC, Michelin PSS, ER cp, aFe filter, CDVx, Vorshlag camber plates, BMS OCC EXTERIOR: trunk spoiler, blacklines, black grills, IND goodies INTERIOR: Alcantara steering wheel, steel pedals, custom mats, MPower e-brake.