Decisions, decisions, decisions

@bipod72 I had Vandersteen 2CE signature IIs for a number of years before moving into a smaller home, where the listening room simply would not accommodate them. I auditioned a boatload of stand mounted speakers at that time. One of my favorites were the SFs. But, in the end, I chose the reference 3A de Capo speakers with the matching stands. The primary reason I made that choice is that the design shares elements of Richard Vandersteen‘s design of the 2CE’s and the sound resembles the Vandersteens. They use proprietary drivers and have no crossover circuitry; there is only wiring to the woofer and a single filter between the amp and the tweeter. I’ve been listening to them for eight years, and remain enamored of the sound. If you prefer the Vandersteen sound, I encourage you to consider them. They are well within your budget, particularly if you can find a used pair.

Thanks again everyone for the advice. I've a lot to consider as I forge my upgrade path especially with regards to additional speaker recommendations and pre-amp/amp options as well. 

@bipod72

Your choice of possible speakers is right on. Other options listed here are great as well.

I approach audio from a "bang for the buck" perspective as well as "risk factor(s)." It appears that the "little" Marantz is going to be part of your life for a while longer. The amp would definitely benefit from power delivery upgrades, starting at the wall socket and working its way to the power cord on the amp. You don’t need to go crazy with this. Things in the "$100 range" can make a notable improvement. When added together can result in (very) significant sonic improvements. Along this line, I would take a good look at your power conditioner/surge protector. A good test is to plug the components directly into the wall. If they sound better, then I’d be looking for something different in power distribution. I’m expecting some push back from those who are not fans of the items mentioned here. This is where the "low risk" element comes into play. If you can borrow these items for home audition (not so easy on wall outlet) you can listen at your leisure and make informed decisions. If they don’t put a smile on your face, then you can return them. (There may be more music in the Marantz than you realize?)

There’s more good news here. These items mentioned are "transportable." When you get your "forever amplifier" they will help the sonics of the newer/better amp as well.

Good luck.

Both very good. Apples/oranges. You get to choose.

A beefier good quality amp can always only help. 

When I was shopping amps for my speakers I really didn't start to hear a difference until I stepped up to a Krell KAV 300il. I already had a B&K 4420 and multiple 150 wpc amps from virtually every 'mid level'  Acurus, Sunfire, Nak, Nad, the list goes on and tbh I think the only time I heard a difference was when musical peaks drove the amps to clipping.

I never 'got' the Vandy sound, but always see their room packed at Axpona and appreciate they're doing something very right to have built such a large, loyal fan base. If I have the choice I'll always buy used and less than 10 years old speakers b4 paying anywhere close to retail. I'd likely wait until a pair of SF came up used.