If you are sure that at the first time your needs requrie a lot of webhosting better to have a look at VPS, or half of dedicated server or something like that.
Have a look at:
http://www.myriadnetwork.com/services/vds.php <VDS offer.
http://vpshosting.net/ < VPS offer
http://www.webhostingbuzz.com/website-hosting.shtml?host_semi-dedicated-hosting < semi-dedicated offer
http://www.ndchost.com/solutions/hosting/semidedicated.php < semi dedicated offer
Have a look at:
http://www.myriadnetwork.com/services/vds.php <VDS offer.
http://vpshosting.net/ < VPS offer
http://www.webhostingbuzz.com/website-hosting.shtml?host_semi-dedicated-hosting < semi-dedicated offer
http://www.ndchost.com/solutions/hosting/semidedicated.php < semi dedicated offer