Dedicated, VPS, Or Grid

I'm attracted to the luster and flexibility of the grid server world and have spent time with on the phone with ENKIconsulting.net (great people) and Mediatemple (salesy people).

ENKIconsulting.net is out of my price range to start and I have been hearing less than nice things about Mediatemple.

---Situation---

I am launching a site running wordpress blog, php bullentin board, customer service support suite, and amember membership script.

My goal is to have room to grow (very quickly) but start off small/cheap with no/minimal downtime or switching costs involved in migration to a dedicated.

My actual "hard numbers" are unknown... visitors, bandwidth, and page KB size, but what is known is that the marketing behind the launch could draw 1000 visitors to the within a day and up to 10,000 and want to be ready.

My budget is pretty small, and need to stay under 100 a month (during the alpha and beta of the site) but once live money will be much less of an issue.

I'm not a webmaster or server admin, and need excellent customer service from the hosting company (telephone and email) and I'm comfortable to used the fun and easy GUI of cpanel to run the show.

---With the above said---

(1) Is there a grid solution out there that is recommended?

(2) If not, what specifications CPU/RAM/HDD fit my needs

(3) Dedicated? Semi-Dedicated?

(4) Are their hosting companies that allow some degree of scale (RAM/CPU/HDD)within a shared semi dedicated environment?

(5) If not and my resource need jump, how difficult is it to provision and migrate an the entire site to a dedicated box?

Basically I am looking for a strong recommendation for hosting that has a platform that allows quick and easy scalability, excellent customer service, reasonable prices (not cheapest), and a friendly web-admin backoffice.