5.6 seems to be available for centOS--
http://opensourcedbms.com/dbms/how-to-upgrade-mysql-5-5-to-mysql-5-6-on-centos-6-3-red-hat-fedora/
> recently the server has got very slow.
Running out of mem. Let's see:
show variables like 'inno%';
> Im not sure if i should go fool around and install from a compiled package, as reliability is also a huge issue
I'm not suggesting you jump now to 5.6. I'm suggesting you set up a second machine with 5.6 and the same data, optimise and benchmark, then compare.
> The server ran out of ram
So 1gb is not near enough.
Nothing in the tables juimps out as a problem; they look carefully designed. EXPLAIN EXTENDED says the query engine can't do much for any of the derived queries. 5.0 and 5.1 execute them outside-in, which can be costly. 5.6 can do some of them with inside-out smarts.