There's no way around it... you look like a completely different person with the piece. People are going to notice that big of a change. But I've also seen way less convincing pictures posted here that people raved about so I'm not sure why yours are receiving so much more scrutiny (and in some cases negativity). There is a lot of good advice here though.

You could get away with just a topper if you wanted to. Your sides look dense enough. That way you could bring your hairline down a little while still keeping a slight recession in it. If you kept the piece at a similar length to the one your own hair is at in the "before" pics I really don't think anyone would notice that dramatic a change. Especially if you combed the hair forward for a little while.

I think the reason people are noticing is that you haven't just changed the shape of your hairline. You've changed the density, length, and style as well. For your first piece I'd try and stick as close to your own hair as possible. For ex, I think something similar to this would look great and very realistic on you: http://z.about.com/d/menshair/1/0/K/0/-/-/adam3.jpg

Then as time goes on you could transition into longer styles or even that full cap. I really think your problem is just too much all at once. But that's just me.