I've got a Sette and a Profitec HX machine (Profitec 500). Been down the road for about 1.5 years.
I have found it is a rather expensive hobby and appears to be no way to make it less so. (buying new)
If your goal is to experiment with espresso and really delve into this hobby, I'd get a Niche Zero grinder. Big review on it here at HB and generally very positive reviews by owners. People say the grinder is the most critical element. The Niche is not available here in Canada and so I went with a Sette.
The Profitec Pro 500 HX is a great looking machine, but has lots of downsides, technically. At least the one I own does. Because of how an HX works, the PID does not control the temp of brew water. Advertising will lead you to believe that the PID will make it more temp stable. Maybe, but you have no idea what that temperature is; and once you start flushing, you add all kinds of variables into temperature stability. (I find you still need to flush occasionally). There is no way on these machines to measure the brew water temp and so you will need an external thermometer in the group to aid in learning the thermal characteristics of your HX machine. ($100 US extra, $200 in Canada). Even with this, you still will have no absolutely verifiable way to know what your brew water temp is without a SCACE. Now people will say you set your temperature by taste, but I don't believe it is as easy on my HX to pull consistently repeatable brew water temp shots. Also, on my Profitec HX, after I pull 2 shots, the brew water source (thermosiphon with restrictor) is slow to recover and I need to wait 15 minutes to pull shots 3 & 4. So this is not a machine for a party (even though it is $2500 here in Canada). (and experimenting takes a long time if you need to pull, say, 6 shots) I think other newer HX designs which have PIDs and a restrictor in the thermosiphon are similar. So I, personally, would not recommend the current HX designs that use a restrictor in the TS loop.
I think the Profitec 300 with its saturated group and DualBoiler design will give you better brew water temp stability and likely the ability to pull more shots in a shorter period of time, but it has weaker steam than the 500 and a lot less steam pressure than the 2 Bar you get out of the newer 700. Only the 700 can do flow profiling but now you are at some serious money.
I think the next few years will bring significant change as manufacturers (I hope) will add more data sensing options to their machines and give you more control over the brew water temperature and pressure (as the Decent DE1 models do).
Right now, from what I read, the best bang/buck is the Breville/Sage Dual Boiler (920) model, which is only about $1000 USD. Some criticize that it may not last as long as the 'big metal' machines, but many owners love them. The Decent DE1+ gives you some incredible control in a pump designed espresso machine. The Bianca has a great review here as well.
The lever machines are really interesting and I personally would love to try one, but have spent enough for a while. Here you can control flow/pressure by manipulating the lever. Currently I'm looking for a really good grinder next, then hope to get a machine like the Decent, or some better DB, as designs improve. I'm not sure I'd go with an E61 grouphead design. (Profitec 500/600/700). Any E61 takes about 45 minutes to warm up to use. Really sucks when you've decided, all of a sudden, you'd like an espresso and you look at the dark power button of your machine. But generally I plan when to have espressos and use a remote controlled power switch and can turn on with my phone.
All this being said, I still really like the espresso from my Pro 500 HX. Maybe my palate is not that developed, or I don't experiment enough (or temp stability in brew water is not as important as I think). I also drink a lot of milk based espresso and the milk will hide some flaws in the espresso.
BTW, the Sette 270 I have has worked very well and is a competent grinder and has very good customer support (from what I read) in North America. It is loud and can't do pour-over coarse grinds. From what I read, the Niche is better. But I have no experience with it. I am currently looking at a used Monolith Conical from Kafatek.