I wonder, do you regularly run your Onan as the manual calls for? I think it specifies to run it under 1/2 load for 2 hours once a month. This will go a long way toward making it reliable. It helps get the moisture out of the windings and the engine. It also helps fresh gas stay in the carb.
Any $300 generator will be extremely loud and probably rather cheaply made. If you're tired of repairing a generator a cheap one from Amazon doesn't sound like a step in the right direction.
A good portable will run you close to $800 for a 2,000 watt. If you want 2 of them for 4,000 watts or just a 3,000 or 4,000 watt generator than a portable will cost you close to $2,000. Any thing less will be loud, burn lots of fuel, and turn your camping neighbors into enemies.