O ring performance is based on they type of paint and thinners used. I believe H&S has converted fully to teflon, or teflon coated rings now, so there is less of a chance of hotter thinners eating them up.
Acrylics, well I haven't change the rings in my Infinity since I have gotten it, and they are still like new (maybe that is a sign I should paint more).
Geegad, if you are looking at around $200, they make an Evolution Silverline 2n1 fPc.
http://www.germanairbrush.com/evolution_silverline_2in1_fpc.html
Biggest difference between the Evolution, and the Silverline is that the Silverline adds the knob at the back that you can screw down, to limit your trigger travel, so say if you want the same thin line every time, you can screw the stop in and the needle will only come back that far. The Silverline fPc adds the fPc valve to the air stem, basically giving you fingertip control of your air pressure, instead of having to adjust it at your compressor. So basically set your compressor to say 30psi, and then just adjust the air valve on the airbrush.
The Silverline 2n1 fPc also comes with the .15mm needle/nozzle (as well as the .4mm) instead of the .2mm that is found in the Evolution 2n1, and the regular Silverline 2n1. The Silverline 2n1 fPc I sell for $206.75, and you end up saving about $30-$40 over buying the Solo and then adding the other parts. The reg. Silverline 2n1 is $186, so for an extra $20, they replace the .2mm, with the .15mm, and throw in the fPc valve which is about a $48 value if purchased separately.
The Infinity Solo runs about the same price as the Silverline 2n1 fPc, and the Infinity 2n1 is about $275. It also has the trigger limiter, but instead of having to screw the knob in and out, you set the limiter to where you want it, and push the button in to lock it, when you want full travel of the trigger, instead of screwing it back out, you just pull off the lock. It is a little more convenient than screwing the knob in and out on the Silverline, but does the same job.