I have an Infinity and it's a great grinder and IMO it will work with pretty much any machine out there. Just look for something in your price range with the features you're looking for and go for it. Some machines are better at steaming than others if you're into lattes, cappas, etc. Myself, I found a barely used CapressoBAR 351 (pump espresso/drip) for $65 including tax and my Infinity goes well with it. Good luck. Later!
What kind of budget do you want to work with? I ask because that will be a good way to narrow your choices. Of course you could consider going used which would extend your buying power if you are willing to take that risk.
I think any Gaggia will work just fine. From what I've read pretty much all Gaggia machines use the same internal parts, just different materials externally. Of course something that's wrapped in stainless will be higher than plastic, but both work the same. Main interest in the Gaggias is the well built grouphead and portafilter. Only problem most complain about is the aluminum boilers used in them. IMO it doesn't matter what type of metal alloys are used for something like this. All will eventually corrode to an extent. Just use high quality softened water in your machine, descale it often and you'll be fine. Later!
BTW, before I bought a decent machine I used a DeLonghi steam machine (which uses an aluminum boiler) for at least 7 years. I used softened, balanced (proper PH) water and cleaned it every month or 2 and the internal parts looked like new when I gave it away. It all comes down to how you take care for something.