So, after all these years, I'm finally the owner of an Amiga 3000 that I bought from someone on Amibay!
Congratulations on your A3000 purchase. I have had one for a long time now and can make a few comments....
Mine is 16mhz version of the 68030. And has the upside down kickstart mounting. It has been upgraded with A3640 V3.1 (manufactured by post Commodore company; Amiga Technologies. So this is 68040 25mhz w/ integral FPU. Card runs perfectly and a great performance added for reasonable price. The only real complaint I have for it is its physical mounting. As in it being just underneath the drive tray. I have a custom heat sink w/ fan to keep things cool. My machine still only 2mb chip / 16mb motherboard fast. Wish I had more. ZoRAM 128MB or 256MB are available. I do not have this though. As I understand it, speed will be limited due to Zorro Bus and not fast like what some accelerators have. I updated the main chipset to latest revision chips. It was a matter of principal I guess. I am not Amiga savy enough to explain any benefits to doing this. I run a GVP Spectrum 24/28 video card. RTG video makes a great experience in my opinion. I also have an XSurf network card. But have yet to hook it up to internet. So for now I just use it for its clockport; Subway USB. USB on an Amiga is awesome. Works like a charm for thumb drives. So for me it is my primary tool for transferring files from the outside world into this Amiga. The best USB solution is the Deneb card though, much faster. I upgraded to a 1.76MB floppy drive as a matter of principal. I hate floppies and only used for software install of my various hardware upgrades. I did run an Elbox FastATA IDE controller for a while. It ran with no issues. I have an external drive box that houses a cd/rw drive. Lately I have just been running a hard drive only from original SCSI, which works just fine of course. For the OS, I use a nearly stock 3.9, I have been meaning to get in there and massively update/patch it but have not had the time.
The 3000 is a great machine in my opinion. Sure it is not AGA but for my own uses, RTG gets me by just fine. As far as I know, the Indivision ECS could be added to this machine. I guess video upgrades are a matter of individual choice. I keep this thing running but do admit to exploring other Amiga alternatives. I think if I ever bought another real Amiga (probably will never do) it might be an A1200 which has AGA and very good upgrade hardware support.
Enjoy your 3000!