10s on a manual transmission is also MUCH more difficult than on an automatic transmission.
And as far as what kind of dyno numbers? It's very hard to say. With '325' rwhp, I went 12.57 @ 109.51 mph. With '335' rwhp, I went 12.09 @ 117.49 mph. In other words, I picked up 8 mph in the 1/4 with '10' rwhp..... Get away from the habit of associating dyno numbers with track times, ESPECIALLY elapsed times; trap speeds are relatively easy to get, but a good ET requires a lot more than just power.
All that being said, a 3600 pound car, with a good suspension/tire setup, good rear gear, stall converter (if an automatic), and most importantly, A GOOD DRIVER, will go 12s with 275ish rwhp, maybe a little less. It will take around 500 on the same car to go 10s.
At the same time, here's what a 650 rwhp car looks like with crappy tires and a crappy driver:
i.e. he got smoked by a car making HALF the amount of power.