Hello, not sure what the forum rules are on this so please correct me if I am off basis.
It does not seem like you need a dedicated solution to me, you have a few sites that survived well in a shared enviroment until now.
Like mistwang suggested Directadmin is your best choice for an optimized control panel.
Like the previous poster stated Softlayer is a great datacenter, in fact they are ex employees of theplanet which another person here recommended, but softlayer did it better. We currently host all our customers in Softlayer and have never been happier.
In regards to your needs, we currently have several servers which have been sub-devided into what we call Virtual Dedicated Servers and not the more common term of VPS/Virtual Private Servers.
The difference is VPS providers oversell their resources in order to offer extremly low price points which in turn leads to degraded performance and generally gives the customer a bad perception of what Virtualization is all about.
With Virtual Dedicated Servers we have built our servers with massive specs and sub devide each system into a set of customers so you get every last bit of resource that you pay for. This ensures that your performance will not degrade and you will not be affected by other customers.
Another benefit of this is that you will be able to scale your websites as you grow, saving you money upfront. If at any time your websites do require the power of a true dedicated server the VPS can be live migrated to the new server with little to no downtime.
To speed up your sites even further and enhance the reliability of your hosting if you choose we can host your VDS from an iSCSI array. Which is 100+ Disk SCSI Storage array.
I would be glad to discuss pricing and help you get setup with a solution that is not only more affordable than what you are currently looking at but will better suit your needs in terms of reliability, performance and administration worries.
Please PM me if you are interested.