I deffinately agree with upgradeing the filtration even if you get away from the O's and the pleco. both are notoriously dirty fish. the JD shouldn't be as bad. but also imo a potentially dirty fish. personally i think your fish are underfed. if their stomachs are concave, look from the base of the tail to under the pectoral fins. Then they are indeed. they should have an overall even contour. nothing can replace WC's they are a neccisary evil. but upgradeing your filters, lowering your bio-load can decrease the amount needed, or adding a planted refugum system. also if your not enjoying the gallons per wc. spread it out. do 25% 2x a week instead of 50% ect.. or the 1 cup a day. it is better then nothing though personally I still have found a major WC is needed when doing anythign less then 10% = 50% a week.
if money is an issue, I'de get another similar filter to what you have and run them both. it will increase your electric costs and filter costs abit. but it is a "quick fix" that is doable. personally I also prefer running 2 filter opposed to simply 1 on a tank and I clean them alternately. every 2 weeks I clean them back and forth so they get clean/changed 1x a month per filter. It allows for a stead BB count to be maintained with little worry or fuss. particularly and on heavier loaded tanks where a crash of bacteria would wipe out my tank in short order due to nitrate/ammonia output.
I too have a planted tank.. and adding plants to a system is a good way to control nitrates but to grow properly they need quality lighting, even if its low light plants, and other nutrients that either need to be dosed, or come with those weekly water changes. I use java moss to help nitrate control and keep baby fish safe in my smaller tanks. they are alot easier then my "planted" tank but they still require some work. to me this way would only be adding more work. for minimal gain. If you want to go the plant route because you think their cool I'de deffinately agree it can help your tank. But if you want to do it "just" to make less water changes on your tank.. imo your asking for more trouble. not to mention if you don't maintain those plants they will decay and make a bigger mess then your already trying to control.