Great advice here from
@pmuller9 and
@63 Sprint. Doing this project on a budget means starting at phase one and ironing out all the kinks. If you're happy with the setup, but want more power and are ready to start spending $$, then you can start planning phase 2+. The woeful log intake setup on these engines means that they respond VERY well to a small amount of boost vs trying to pull fuel & air through the log at vacuum. There are folks on here running 5 lbs of boost from a supercharger who are happy with that increase in power and drivability. A 300-400 hp engine is certainly attainable, but it will be expensive. Like they always say, "Power costs money. How fast do you want to go?" And of course, it's going to cost more money for less hp by using the six as a starting point vs a V8.
I have always thought that the abundance of room in the six engine bay would lend itself to a turbo setup quite nicely. Running a 5 psi turbo right off the stock exhaust manifold wouldn't require an intercooler and the whole setup wouldn't take up much room. Using a header with a crossover(under) pipe and mounting the turbo on the passenger side of the engine would allow for even more room for external wastegate plumbing, etc. Once that was dialed in, if more power was "needed", adding an intercooler and upping the boost to 8-10 psi could be the next step, and that would set up the foundation for later mods, like a cam, built block, etc.
I used to have a supercharged, flex-fuel swilling Infiniti G35. First phase, we built it to about 420 whp. It was a lot of fun, and my daily driver. Then I got used to the power and wanted more - cue phase 2: smaller pulley, lots of tuning tweaks, now about 480 whp. Now it was a riot. But of course - I got used to the power and, you guessed it, wanted more. On to phase 3: built motor, bigger intercooler, even smaller pulley, bigger injectors, more tuning, and a lot more cash. Final result - 560 hp at the wheels. Broke axles. Broke a transmission. Car was now a smoke machine that couldn't hook up the tires even with drag radials because the rear suspension was not built to handle anywhere near that level of power. Long story, but the point is that there is such a thing as too much in a regularly driven street car. Depends on what the chassis and driveline parts can handle. That car was an absolute blast at phase 2, and unmanageable at phase 3.
None of this is meant to dissuade you from pursuing a turbo project - I think it's an awesome idea and have fantasized about it many times myself. Just be sure to plan a realistic project for your skillset, budget, and needs, so that you don't get discouraged halfway through. This forum is a wealth of knowledge and encouragement, and as you've noticed already, there are lots of people here willing to help, from planning all the way to completion and beyond.