If you could swing a Rega IO and a pair of Monitor Audio Gold GX100’s you’d be off to a really nice start... I’d make sacrifices for a few weeks if I had to, as in use my phone with a 3.5 mm cord and no dac until I could get a Bluesound node 2i, then I’d use the dac in the Bluedound until I could get a better dac like a schiit bifrost multibit or whatever and then you’d be sittin pretty.
I think Monitor Audio Silvers would be my choice (and a good one!) in the lesser price range. Q acoustics, kef, dali are all great speakers as well but I feel that the Silvers are best in that price point. I had some Gold GX50’s and loved them. They are just built so well. Silvers look to be really close. The bolt thru drivers are a cool idea and unique to them. Check out those bolts on the backs of the speakers. Those contect to the drivers and hold the drivers in the cabinets that way. The drivers, cabinets, internal wiring all looked really nice in my Golds, like really nice.
As stated above about the differences in the models, as you go up the line they get bigger and with more drivers / bigger drivers.
I’ve found that the 7” drivers can handle more abuse or louder volumes than the 5” drivers. Take this into account... I had paradigm studio 60’s that had three 5 1/2” drivers. I also had the Studio 20 which had one 7” driver. Both were from the same generation, v5. The 60’s sounded awesome and had slightly more dynamics at low to medium levels but the 20’s could play louder and stay composed at higher volumes than the 60’s. Paradigm makes a studio 100 that uses 4 of the larger 7” drivers which would have overloaded my room so the only way to get “more” within the brand was to move from Studio 20’s to S2’s.
Point is, if you like to crank it up at times, the 7” drivers are better. If you are always listening at quiet to medium volumes, sometimes the 5” versions are better because all other things equal, the smaller driver will be faster and the thinner front baffle can produce better imaging. A thin, tall speaker is pretty sexy too.
I don’t think you have to worry about much when buying speakers preowned at this level (just do your due diligence with the seller) and I think you can save some $ doing it that way. Preowned integrateds in the $500-$700 range aren’t going to offer much, if any, over something like a new Rega IO @ $500 and buying electronics new is reassuring (warranty etc).
When looking at speakers remember that stands are going to cost $150 so that eats into a savings you have with a standmount vs a floorstanding speaker.
Good Luck and have fun!