Can le, stock 325i on the crank is already 195hp, let's assume 20% transmission lost, 156whp.
The stock M54 intake manifold is super restrictive, swapping to another M52B25 intake manifold will add approx 10hp without tune. Doing other basic IHE mods, stronger ignition spark, spark plugs and lastly flashing the ECU, might be about 200whp, but also depends on what dyno you are running on to see the figure lo. Most importantly is on the road feel.
Buy E46 + mod.. better just buy the E90 right? You get a better chassis and a better transmission.
Remember children about the story of #bmw1jzparking