The RB26 seemed to me like a good deal, but it was way too expensive. MAINLY because after getting the 26, I would have to go find the RB25 transmission which would be roughly a grand, sometimes more. (That would be about 4K+ for Motor and RB25 Trans) I bought my RB25 for 2K.
Also, my reason for getting the RB25 was the fact that it came in ECR33's (1995-1998). Most RB26's that are stateside come from BCNR32's (1989-1994) [Please correct me if I'm wrong].
I didn't want to put myself in the situation of having a motor from 1992, so I opted out for a newer RB25DET (not that much newer, but still newer).
The GReddy manifold is not a needed part, but I like the fact that it's a huge plenum that doesnt wrap over the valve cover. Reduces a lot of piping to increase throttle response.
So yeah, I probably could have done other things... but to each his own Z.
-Cheers
P.S. - I'm also saving up and buying all my parts before putting them into the car. Very good idea saves money and time in the long run. Especially clutch and flywheel!