Where to start upgrade

Trying to decide where to start upgrading my system. I have a pair of AV123 Strata Mini's, they are powered by a Elite series Pioneer SC-25 receiver, also using an Escient Fireball E2-400, using the pioneer's D/A converter. Mostly thinking of upgrading one of these three, any suggestions on the speakers or receiver would be helpfully. If I upgrade the music server(fireball) I think I'll go with the Olive 4HD.
Although impractible and overly expensive you will likely change both your "receiver and your speakers. If you can audition either of the speakers you are considering or their amplification I would do that . What do you want? Are you looking for another receiver or are you interested in high grade amps to improve your sound. If you want an amp you probably would be happier with an integrated vs. separates. Then you have to give us some idea of how much you want to spend and the type of sound you want.
Same goes for speakers. Budget? Style- monitor or floorstander or ? built ins? etc. Most people will say that the speakers matter most and I don't disagree but we need more info to help you.
Buy a great pair of speakers (for your listening space) and then SUFFER.
anyway, that's what i did. Just looking for an amplifier you can afford can really drive you nuts. the only break you might get is there is plenty of inexpensive used wire available. and you don't have to worry about power cords either.
but just about everything else matters a lot.
Frenchie nailed it.Spend the majority of your budget on the best speakers you can afford.The Elite has plenty of power & pretty decent sound.
Once you have a great pair of speakers,a good Integrated Amp would be next...
One of the most important "matches" in audio is the amp/speaker combo. When this match is properly acheived the system sounds like it is something more than just the sum of its parts and, if you ask me, that's where a lot of the magic is. I just would never contemplate buying one without first having given considerable thought to the other as a suitable match. It is possible to achieve very synergistic levels of performance that are both acurate and yet musical for modest amounts of money. I know. I've done it. The biggest hurdle seems to be the amount of time spent in pursuit of the result, but, if you are willing to roll up your sleeves and do the homework, you can get everything you want at the right price. Remember: if there's something about a prospective piece of gear that doesn't fit with your overall goal, tentatively cross it off your list and keep going. Go ahead and be thorough in your search and let time be on your side. I myself use a pair of Monarchy SM-70 Pro amps as monoblocks and I installed a pair of Goldpoint series attenuators inside the rear panels - all of which would very likely be asking a lot technically of someone who may be essentially just starting out, but the preamp/amp/speaker combo (minus the wiring) in my rig was only about $2,500, yet it's very revealing. The good deals and good combinations for you are indeed out there, you just have to begin by convincing yourself from the outset that they do in fact exist and by giving yourself time enough to unearth them you'll be ahead of the game. That, and learn all you can about what makes a good system as you go - all part of the fun, really. Hope this helps. Regards.
Your most effective upgrade begins with your listening room. Disclaimer ... I'm a dealer. But I'm altruistic when it comes to our hobby. I won't push a product on you but only share my personal experience. The merry-go-round stopped when I fixed the room. I tried all the traditional treatments since the early 80's. One of the biggest head shakers was learning that some gorgeous absorption products that are found in studios and music rooms for many many years has a reflective fabric. So when testing the fully treated room we were still seeing significant bass nodes only to learn the lesson of the fabric used. It's from the same company that supplies nearly every acoustic treatment company out there ... it looks nice ... but the money was spent on a cosmetic solution and not acoustic.

If you're good to go with your room then i completely agree with the prior responses.

Enjoy the journey to a better room.
I have been "upgrading" since I was 14 years old....the MOST expensive path to audio perfection.