I just thought I'd pick up on your comments about the turbo button of old.
The turbo button, as I recall, actually took a stock processor (like a 486 sx-25 that ran at 25MHz normally) down in speed, due to some programs not running properly on such 'fast' equipment.
One example I remember was Wing Commander in the gaming community, it got so fast that within half a second of a mission loading about 50 asteroids zoomed there way past the screen blowing your ship to crap before you even had a chance to operate the controls. The 'turbo' button was needed to slow the machine down so you got a normal and playable framerate again.
IMO you would not notice the difference between 3.4GHz and 4.6GHz whilst using normal desktop apps, you have to be doing something very CPU intensive to see the difference and that will come in something like gaming or an operation where you can see a progress bar move that takes N seconds, which could now be done about 25% faster with the overclock (assuming it's not bottlenecked on anything else in the hardware like disk).
Probably the most expensive CPU task you'll have running from those mentioned is the database, but if the queries it is doing are for realtime responses (OLTP style) this would also be so fast as to not appreciate the difference. Compiling may benefit but that depends on the size of the code chunks being compiled, 20k line apps or chunks would be a blink of an eye, 5 mil line apps could see a notable increase if compiling the lot at once.
Additionally, for the small bursts of cpu processing power, that may only last a second or less but be perceivable to you as being a moment of slowdown, the processor does have 'easy mode' overclocking built in where the CPU will 'turbo' itself up to as much as 3.8GHz, without you having to even press a button, and then lower itself again when the task is done or it can't sustain that setting any longer (heat/voltage).
Actual overclocking isn't particularly reliable ever, whenever you go outside the envelope and stay there, strange things can just happen (I've played multiple games end-to-end, movies, installed stuff, left it idle, done desktop stuff, for several hours of several days in the past week without any hitch, maxed single cores, maxed multiple cores, yet today I got a BSOD totally randomly - I am positive this wouldn't have occurred without an overclock in place). The programs make it easier to overclock, they don't make the machine any more reliable than the settings you're willing to push it through.
In terms of graphics card, anything would be fine for the purposes you've mentioned, even the on-CPU one.
