Gotcha... A metadata-based file browser wouldn't work so well, would it...?
I was lucky with my ripping (this is beginning to sound a bit like Clint's speech in 'Unforgiven'...); for starters, HDDs had fallen in price such that a 1.25TB drive was reasonable, and I decided from the outset to rip lossless (a number of my friends regret ripping to lossy formats, but can't face the re-ripping task). I wasn't online then, but I did have a big file of metadata for most of my collection, with disc details and track titles and durations, all laboriously entered by hand, starting with my trusty Sinclair QL computer... It was in a semicolon-separated format, so easy to parse with AWK. So I used those details, and wrote my unix scripts to take the album metadata file, parse it, and create a renaming script that could be run after ripping (without needing to enter any metadata during the rip, other than album artist and album title, to make sure it got saved in a unique folder). I'd developed my own metadata format preferences over the years; they are subtly different to those usually adopted by freedb entries.
That system continued even after I got online, as the public databases were generally pretty poor, and it took as long to check and correct metadata before I ripped, as it did to type in the metadata whilst ripping. Now I have a 42x CD drive in my computer, I can't type it in fast enough, and the metadata sources have improved. So I have largely stopped manual entry of data.
I have other media sources that aren't so well tagged. And those have taken considerable effort to identify and get good artwork for. The latest OCD process is to refresh the artwork with 1200 or 1400 pixel images that are becoming available; I scanned to 300dpi, and resized to 600pix square. I kept the original, though, so I'll soon be running a script to copy the larger images into the CD folders, whilst retaining any newer artwork I have downloaded (an idea on how to do that has just popped into my head)...
Poor man's NAS is exactly the approach I first suggest to people: see what your existing equipment can do. I bought my NAS before I was online, so I use that, but my router does have a USB port that can support both file server and DLNA media server. I did have to spend quite a long time figuring out how to get the NAS DLNA server to work properly without getting broken every time I touched the NAS. I wrote up my findings on the WD forum, and that thread has now accumulated about 120k hits...