Hi Bgary335
I don't think you're being unreasonable. If I had paid big bucks for my collection I would have much less of it. Some it jumped into my lap.
I think you are after a controller and memory expansion as well as a hard drive. The expensive controller is GVP's models. Supra made the XP, would take upto 8 Megs of ram and a SCSI HD, SCSI CD drives (in seperate case) could be interfaced to the back. I don't think they support DMA, but still very usable. I have one of these and see them on eBay regularly, it seems in the price range you want. I think the Supra XP is compatible with their Turbo 25Mhz accelerator, too.
It can be discouraging when people (wise and well meaning, of course) tell you that your lowly machine is only good for retro games in this modern world. There are other ppl here who do amazing things with simpler systems. I have surfed the net with an A500. It wasn't fast, but very gratifying to use a 20 year old machine this way! There is room for many perspectives on this site.
I say listen to your passion for the machine and selectively to some of the "common wisdom" routinely dished up here.