To me the math on 160 DVDs works out like this:
Based on your calculations, you're planning on ripping them directly at full quality (no re-compression) to your multi-drive Mini. That saves time, though it would still take about 40 to 80 hours to actually get that data onto the drives (4x or 8x DVD read speed), and you're going to need 1.2TB of space (plus overhead for the future). So you're going to be paying $600 (mini + wireless) + $1200 (3 Lacie 500GB Big Disks) = $1800. Or, go with one of the new Lacie Biggest Disk 1.6TB (or preferably 2TB version, which you can use with RAID5 so you don't have to re-rip everything if one drive crashes), which will set you back $2300 or $3000 respectively.
Alternately, you could get a $310 Sony 400 DVD changer, load all your discs into it (an hour?), and be done. Or, if backup is your worry, assuming roughly $10 a disc for TV series box sets (maybe too cheap), you could buy an entire second set of DVDs for about $1600, and you're still only $100 over the cost of the bare minimum Mini-based system, and half of a cleaner one.
Then again, if money is no object, then who cares about backup or which is more expensive; the 400 DVD changer will save you 79 hours loading movies, and will probably work better playing them back, plus it will use way less energy and make a lot less noise (those external drives aren't as quiet as the mini) if you leave it on all the time.
The alternate option would be to rip all the DVDs in, say, XviD, where a couple hours of video takes maybe 1-2GB of data, depending on how much of a stickler for quality you are. Assuming 500MB/hour, you could get by with only 320GB of hard drive space, so a single 400GB external Seagate would only run $330, bringing the total cost to under $1000. Except at 10+ hours to rip a disc, it would take you 80 days to finish. Again, the $310 Sony seems like a much more efficient solution, and you could still buy the Mini to go with your TV for other purposes.
Don't get me wrong, I love the Mini, and I want one to hook up to my TV as a media center, too. But trying to use it to hold 160 DVDs just seems like a waste of effort when there are far cheaper, less time-consuming, and more effective solutions available for expressly that purpose.
Oh, and the difference between ripping your CD collection and your video collection is that songs are 4 minutes long, something you turn on walking by on a whim, play in the background during other activities, and people love to randomize them or mix and match them. Plus, your entire collection will fit on a handheld portable player, so you can enjoy it while out and about.
Video comes in at least 30 minute chunks, is generally something watched as a primary activity, isn't exactly something you put on "party shuffle" (which you couldn't do effectively with the Mini even if you wanted to), and takes up WAY more space--a $300 pocket-sized iPod to hold 280 CDs is not the same thing as a $2000+ computer set-up consisting of multiple external disk drives and a lot of work for half as many DVDs.
