i have a 2003 eclipse RS, what kind of motor i can swap it with to get more hp and what motor would be a great fit with room for more upgrades?

All depends on your budget, fabrication skills and free time. Easiest is to shovel in a 3 lite V6 from an Eclipse GT or GTS (6G72), complete with transmission and all ancilliaries. But you could try and squeeze in a 276BHP DOHC twin turbo V6 engine (6A13TT) from a 1996-2003 Galant VR-4 instead, but this is a bit trickier.

You should check out the club 3g forums. I've seen a few guys post builds there regarding adding a turbo to the 2.4 engine. They recommend a head swap to an evo dohc, or a kia dohc head. The stock head chokes airflow at higher rpms. I think you should considered adding a better intake manifold aswell, but keep in mind that a stock block won't make the most power from a turbo. You need better internals and lower compression to really get your money's worth. The cost of a turbo kit, plus fabrication, and a head swap can be 3-5k depending on labor and diy. I would go for an n/a tune, you can get a cold air intake, header,cat back exhaust, laser cut iridium plugs, better wires/coils, and an ecu tune for around 2k. That should get you up to around 200hp with far less issues than a turbo, and prolong the life of the engine block.