2500 Unique/day Seems To Be Too Much

We're actually hosted at site5.com and our 7 wordpress blogs (+1 wp-mu) get about 2500 unique/day... blogs uses a lot of plugins and costumization, but i think we shouldn't have problem with such number of vistitors.
[about 20gb transfer per month and 1 gb disk space used]

Customer service sometimes write about mysql load, sometimes complain about server problems and so on... we're thinking about move somewhere else.

Of course we don't want to move to something like dreamhost and have the same problems after a couple of months and we're not rich, but:

- our readers are mostly italians, so we'ld like to move somewhere in europe, but european services are expensive

- we need mysql/php/... bla bla usual stuff

- we have a lot of domains for underdevelopment projects

- we gave a try to MT gridservice but it was really slow

- we need ssh access

- we don't have time to manage hosting configurations and so on

- we need a reliable hosting service but we aren't google.com

- we can spent AT MOST 20$/month

which you think can be the best hosting service for us? is better to think about a VPS solution?? managed bla bla bla service?