Keyword matching domain names

To make a long story short, this weekend I woke up with a great idea for a domain name. I wake up fire up the laptop and hit google keyword external and do a little keyword research on it having a pretty good idea that it likely had a lot of targeted searches for the domain name that I want to register. Alas, the keyword phrase-domain was taken, but I've got a pretty good feeling about this type of domain if I can just get a really good targetted keyword out of my initial idea. I continue tinkering with my research and find 2 domains available that seem to be targeted and in the area that I'm looking to dip my toe into.

One of the keyword phrases gets roughly 250k searches on google per month, the other has over 1.2 million searches (on the specific key phrase) per month. I check my domain registrar and find that the 250k searches site has the dot-com tld matching the keyword phrase, and the other has dot-net name available. So now I'm in a conundrum. I've had lackluster to moderate success with marketing info products, and this is my first foray into actual physical products but I'm willing to give it the ole' college try to see if this does a little better for me. My monetization method is likely going to be a blog running adsense ads with an attached amazon store handled by associate-o-matic.

My question begins like this. Is there any way to tell how important an exact keyphrase matching domain name is when google is displaying its SERPs? There is a high level of competition in this niche (high end consumer electronics), but it is something that I feel that I can write much easier about than the info-products that I've been promoting thus-far. The last part of the question is more of a consensus poll. In a highly competive market like this would it more advisable to begin promoting, or just develop and then flip the property for a quick buck or two?

Thanks for any and all replies!