For example, Raritan Paragon KVM switches:http://www.raritan.com/UMT2161RK/
(and others on that site). They'll easily reach 50 feet through Cat-5, although I'm not sure what video bandwidth they claim (eg, very high resolution, high refresh video might be asking a bit much). AFAIK they redigitise the video, and send it, so the bandwidth is definitely better than running 50 feet of KVM cables. (It's analogue video though, not DVI, to the best of my knowledge. DVI, sent digitally, would seem more likely to handle high resolution without bluring.)
They definitely work okay for text consoles, and 800x600. One of my clients has one, and is very pleased with it. (There's even a "IP access" module for it which "works" but I definitely wouldn't recommend the IP access for daily use -- it's extrememly handy for emergency access when you're not in the right city though...)
FWIW, at 20 feet, just run good quality KVM cables to a good quality electronic KVM switch. (I've tended to use NovaView, but there are plenty of others; you want one which allows keyboard switching 'cause walking down to press buttons on the KVM switch gets old quickly.) At 20-30 feet, with well shielded cable, text consoles and 800x600 are very usable; I've not had reason to try to push it any further (I just use serial console for most of my servers anyway -- even the PCs). At a guess 1024x768@60Hz would be okay. The good quality KVM switches claim more, but you run into cable bandwidth issues on longer cables.
Depending on your CD-ROM requirements you may well find mounting it over the network as a file share is sufficient. Although in practice I've found in > 3 years of mainly using a single-spindle laptop (ie, hard drive only) that I so rarely need to access CD media that I can stand to walk to the machine room to do it. ("The Internet provides" :-) )