First thing is to get down to basics. Torque is what moves the car. It is what accelerates the car away from the stop light and it is also what breaks parts (if you should happen to have a 10 bolt 8.2 inch ring gear with a 28 spline axles). Cubic inches make torque (which is why big blocks are so popular despite the 0.200 second handicap imposed by their added weight). So you want the biggest big block or the biggest small block you can find. While looking for a bigger motor, keep in mind that a longer stroke also builds torque (but this only applies to Otto cycle engines not applicable with a Diesel cycle engine).
So why is horsepower all that gets ink in magazines and was painted on the hoods of NASCAR stock cars back when they were mostly "stock" cars? Because horsepower wins races (remember you said you want a street driven car). In the case of NASCAR it is horsepower that overcomes the friction of tires, gears and bearings as well as the biggest drag on the car air resistance (fluid friction) allowing them to race around the high bank oval track at a more or less steady speed. In the case of drag racing it is horsepower that wins the race because of how horsepower is defined. It is torque applied over time. Since the elapsed time is all important you want to build a motor that created the most torque at the highest RPM you can twist the motor (RPM is revolutions per MINUTE) it is all about time.
On the street you have nearly all day to get from your house to the car show, or to just cruise for the enjoyment of driving. Keep in mind it takes only seven horsepower (the same level of power as it takes to run your A/C compressor) to push your car down a level road at 45 mph. The faster you go above this speed the greater is the horsepower requirement (it increases exponentially which means a small increaser in speed requires a tremendous increase in horsepower to push the air out of the way. To "feel the power" you need only stand on the side of the interstate as a semi passes you a few feet away (I think they were aiming for me when I worked as a cop). The blast of air pushed out from in front of the truck can nearly knock you over.
Ok you want a big motor that makes gobs of torque. So what goes inside it to make it work? Let me demonstrate graphically (with a picture) the difference between an all forged bottom end (piston rods and crank) compared to a cast piston and crank (all Chevy rods are forged unlike Pontiac and Olds that used cast rods in their low horsepower applications).
First a forged bottom end after something goes wrong:
The block is still useable though it requires one sleeve to maintain the same bore size, or over bore and buy eight new pistons. Point being catastrophic damage but contained because forged parts bend instead of break. Now to look at what you get to work with cast or in this case hyper parts (that are still cast only out of a different alloy).
This was a 383 that someone was proud of that was destroyed by detonation. The point is in what happens when something eventually goes wrong. Forged parts are not stronger than cast, the difference is cast parts break into pieces and forged parts bend rather than break. The store bought crate engines for the most part all use cheaper cast parts instead of forged parts which makes a difference in the final price.
Finally let me address the popular rumpitty-rump noise that race cars make at idle, and everyone wants to emulate. I would first point out that race cars never race at idle (I have a John Deere Model M tractor that used to compete in how slow can you go, and thus ran at idle, which on my tractor was about 45 RPM, and in double low gear hardly moved). Race cars however race at wide open throttle which a street driven car hardly ever encounters. To increase the RPM of their motors they have very long duration numbers. This holds the valves open longer to give air a chance to move in an out of a motor at 10,000 RPM. As much as you may want a rumpity-rump idle it isn't worth the hassle on the street. The duration and LSA for that matter needs to be examined closely. As your displacement increases you need to lengthen the duration for the same reason a race car needs a longer duration, A bigger engine takes more time to fill with air than a smaller one does.