hi there, to be honest anything released pre-2011 will be outdated within a few months, thats all there is too it, new phones this year bar the SE Arc and possibly a few others are shipping with single cores and X RAM, everything else will or should have 1GB RAM and dual core. heck theres even been talks of quad core by the end of the year.
What exactly are you looking to use it for? if you want a PHONE go with any decent one coming out: Galaxy S 2, the Atrix etc
If you want a tablet and you like the Dell Streak Style there is the Dell Streak 7 which is the successor to the dell streak except it has a 7 inch screen as opposed to 5, though does fall short in a few places.