I have an A4000T that has just about everything you can put in it for performance including a CSPPC with 4.1FE running, mediator with all the PCI cards you could ever want, nearly 1GB of fast RAM now and so on.
The latest version of UAE with CSPPC support is amazing. I have been playing with my WinUAE setup all week and making it match the real A4000T. I am using the same install cloned over. I can say it blows away the real hardware in every way. The coolest thing about it is the ease at adding new "hardware" and RAM is endless if I want I to be. I have 128GB on my Mac Pro. I boot into Windows on it for WinUAE and it runs FAST.
I am seriously considering getting a broken Amiga case and putting a modern PC motherboard into it and an interface to use a real keyboard. Once setup properly you can boot directly into the Amiga environment with no windows as mentioned. It feels just like a real Amiga at that point. I have seen others do it, and unless told you have no idea.