HDMI switch box to one long run of HDMI cable

HI, I am thinking of moving all my gear away from the TV and speakers area for aesthetic reasons. I was going to put my amp down by the TV and everything else would go in the back of the room. I am thinking I would need to run an HDMI cable under the floor. I am wondering if the best way would be to get a switch box and run all my HDMI inputs (sat receiver, Computer, Apple TV and DVD player into a switch box then run one single HDMI cable under the house? I was going to have to get a 30ft interconnect as well to run from Preamp to amp. Could I put all of this in one big like 3" conduit or is it better to run then all separate?

Thanks, Ryan
I use an Oppo HDMI switch box in a very simillar situation as what you are describing except I ran through the walls and ran speaker cable to speakers instead of interconnect. It works very well. I went with plenum rated cable instead of a conduit. I was unsure if a PVC conduit would have an adverse affect on sound quality like I have read that synthetic carpet might.
I am running about 20' of HDMI cable and have no problems with picture quality.

Recommend you run speaker cable that distance, not interconnect. Not totally sure about this, but I think you have a good chance of picking up EMI/RFI with interconnects that are that long, the voltages are not that high, you might also get signal loss. 30' of speaker wire would be less susceptible to EMI/RFI because of the high voltage in the line, also cheaper to run, several very good types of speaker wire sold in bulk. Make sure to use a heavy guage.
I run 25' of HDMI, rated in-wall from Monoprice.com, picture looks good. Dunno how much better it would look with uber-expensive HDMI cable, but I'd have to find a pile of money in the street to do the shoot-out. I'm more of a two-channel guy. I don't use conduit either.