I've seen some of your videos, and I believe it's not really the camera that's a major issue with youtube videos, but rather the lightning.
Proper lightning makes a ton of difference and in your videos, the lightning is very poor.
I personally have a Sony Handycam HDR-SR5E bought almost new from eBay and it works great but it's somewhat expensive even today.
Even with this camera that has quite good low light recording, some extra lightning helps. I've bought two of these (but without the motion sensor):
http://www.ebay.co.uk/itm/500W-HALOGEN-MOTION-SENSOR-FLOOD-GARDEN-SECURITY-LIGHT-180D-12M-DETECTION-RANGE-/280973166691from a local do-it-yourself style show (they're sold as garden lights) for about 10$ each, and light bulbs are about 1-3$ each. I've mounted them above my desk on a beam and they really light up the desk when both are turned on.
Being incandescent, they also have the benefit of not affecting the recording with cfl flicker (since they don't flicker) ...some cameras depending on what shutter and sensor they use can be affected by flicker.
This Sony camera doesn't have an external microphone but I'm quite pleased with the surround sound it produces in what i record. So I wouldn't base a camera buy on the ability to record from external microphones.
edit: I would recommend going for one that HAS some kind of lens support (so you could screw lens to get macro mode or wide angle) and one that has a good native/optical zoom.
The Sony I use is quite narrow angle (with the lens built in) but luckily it has 37mm lens support and I'm just waiting for lens to arrive which would make it capture more stuff in the frame (wide angle).
There's a whole debate about going with one that uses a CCD sensor or a CMOS sensor, each technology has faults... I tend to like the CMOS sensors more these days. You can read about both here and make up your mind :
http://dvxuser.com/jason/CMOS-CCD/ you can read a lot about it here Ideally, you'd go for one with a large CMOS sensor, but those are usually more expensive.