I have a Getz that I drive for work, 5spd 1.5L, 360,000km on the clock, and not once have I ever thought it was better on the freeway than my V6 Commodore. Sure, it can hit 110 with no trouble and is perky enough to accidentally float past it with no trouble, but that doesn't mean it's NICE to drive on the freeway.
Long, high speed trips should definitely be done in a big car with a big engine, even if it's not a high end model. I have a VX executive wagon with the only modification being that I've dropped a getrag into it, and I love driving it. City driving, freeway driving, no dramas at all.
If you can get a VX with low KMs at the right price, you really can't go wrong with it (apart from the 4 speed auto gearbox being awful). If you look in the right place, you can get one in awesome condition, too. My dad has been trying to sell his VX SS for ages now, paint is schmick, interior is great (driver's seat's a bit soft on one side is the only problem), and I think he's only got about 160,000km on the clock. Only problem is the SS will probably be out of your price range unless you find one that's in bad condition and not worth buying!