Hey man. Spec V's still only come in 6 speed, if it's a CVT it's a regular SE-R. It's the same physical transmission, but the gearing is different..
1. The B15's gear ratios: (This is for an 06, the Gen 1 B15's were a a bit different, but not different enough to matter for the comparison here).
First Gear Ratio (:1): 3.15
Second Gear Ratio (:1): 1.94
Third Gear Ratio (:1): 1.39
Fourth Gear Ratio (:1): 1.06
Fifth Gear Ratio (:1): 0.81
Sixth Gear Ratio (:1): 0.67
Reverse Ratio (:1): 3.00
Final Drive Axle Ratio (:1): 4.13
The B16's:
First Gear Ratio (:1): 3.15
Second Gear Ratio (:1): 1.95
Third Gear Ratio (:1): 1.39
Fourth Gear Ratio (:1): 1.06
Fifth Gear Ratio (:1): 0.81
Sixth Gear Ratio (:1): 0.63
Reverse Ratio (:1): 3.00
Final Drive Axle Ratio (:1): 4.43
Keep in mind that you can run out the B16 Spec V to 7000 RPM. The real difference is in the final drive.
2. The SR is a 2.0 with SE-R Exterior. They did the same thing with the B15's with the "SE-R Appearance Package".
3. I've driven a few of the newer Spec V's and really like them, and the few people I know with them really enjoy them as well.
4. There's been a few rumors about the new Sentras, the word turbo keeps floating around, but I'll believe it when I see it. There was an article about it, but now I can't seem to find it
Hope this helps man.