For your budget you can lift your whole system, or you can think of the upgrading as a continuing process and focus on one thing at time as you can afford it. When I look back at all the "upgrading" I've done over the past 20 years or so, I find that the times I've stretched to get a really spectacularly good piece of gear have given me more long-term satisfaction than just getting things that are slightly "better." The risk is that you won't get the real benefit of some great stuff until the rest of the system is raised to a similar level.
For instance, the Maggie 1.7's is a great suggestion, and you could definitely spend a few years getting the rest of the system up to the point where you can get the absolute best from them that they have to offer.
OTOH, if you have some specific things you don't like about your current system, then I'd recommend that you focus on fixing those things first. What gives you the most pleasure might be pretty different from what floats my boat, or others'. So you need to decide what you are trying to achieve -- set a specific goal -- rather than just buying "better" stuff.
Um. System. So there's synergistic effects that can make the whole of the result from a system much more satisfying than what you get from individual purchases. For instance, MagTech/Sandersound amps are spectacular partners with Maggie 1.7's. BTW, you might be able to get close with a pair of used Maggie. 1.6qrs + and a used Innersound 300 ESL amp (also Roger Sanders design) for about your $2500 budget. Maggies love power!
IMHO, you'd get more bang from the speaker end first, but ultimately the front end will really determine your enjoyment. But there's a risk too. Doing new speakers first might frustrate you by over-exposing the weaknesses of the rest of your gear. The paradox is that you will not get the full benefit of front-end improvements without the speakers to realize the gain. And vice-versa. And so it goes.
If you do your homework, listen to other systems if you can to better understand what's possible, you should be able to figure out where you'll get the most joy. If you already like your system sound, maybe the best use of funds is to buy more records!
Hope this helps.