I hate to be the one to throw another spanner in the works here... but there is still going to be a difference in picture quality Component HD vs HDMI over 15m. A decent HDMI 15m cable wont cost you more than R1800, which, yes, might be pricey, but its going to give you far better picture that component.
If anyone wants to dispute this and has a HD PVR you can test it yourself. wire up an HDMI cable to the HDMI out, and to the Component out. Bring up the EPG or info bar and have a look at the quality of the picture - massive difference. Its a basic test and yes, there are many other factors to keep in mind when running a 15m HDMI cable, but I'll be honest in saying I've personally installed 15m cables at least 3 times and have had no problems whatsoever...
What are you using for your video switching - are you going via a AVR? or just straight out the DVD player?
As much as I will probably take flack for this, but the PS3 is still a bloody good unit for both DVD and the added bonus of BluRay, and then also you get to play games on it and use it as a media server. Try PS3mediaserver - google it - it works like a charm to stream things off your network to your PS3 - like all those series you illegally download at work! (

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but...if you are sticking to the component route, 75ohm cables are the way to go as per what Kenmasters and Ludo said. And the Tosh players are pretty good bang for your buck. (I just wish i had bought a few of their HD-DVD players a while back - all those titles on HD-DVD went for so cheap when blu-ray officially took over; could have had a HUGE HD collection for a fraction of the cost!)