I've been leaning towards the forester based on what I was reading here but because I'm buying used and on a budget I might just settle for the best deal I can find. Also due to my budget, the vehicles I was looking at were in the 2000-2005 range.
Go for the newest, cleanest car you can afford with the best service history. Kind of a generic rule of thumb in buying anything, but it definitely applies here.
What kind of thing should I look for in regards to the head gaskets and how much would repair or replacement of them cost?
Expect head gasket replacement to typically run $1500-$2000 depending on where you have it done and what else you do at the same time. If you're tearing down the engine to the point where you're replacing the head gaskets, you may as well also replace the timing belt, tensioners, and water pump since you'll have access to them as well. The EJ25 is an interference engine, so if the timing belt goes pistons will eat valves.
Use OEM headgaskets. They were redesigned somewhere in the 2008 timeframe to mitigate the weep issues they had up to around that point, and some of the aftermarket ones don't quite match up. If you're going to be in the job for the amount of money you're potentially looking at, it doesn't make sense to save $30-$50 on the aftermarket parts only to have to tear it all down again in a couple of years for the same reason as the first time.
Lift options are somewhat limited for these vehicles, and don't expect to go much over 2" without starting to stress the CV joints. Not many options for regearing, either, so with larger tyres performance and fuel economy will be affected.
The usual lift methods are spacers on the strut tops, lifted springs, or a combination of the two. Check the
Suspension and Handling forum for some ideas as to how to do this; if you've any specific questions, bring them back here and we'll do what we can to help.