How far is too far

Software based clocks are always going to be very much on the side of caution, I used amd overdrive and couldnt pass 3.2Ghz on my rig, read a couple things on here and im at 3.5Ghz and have room for more should i wish to   read a few threads on here for your mobo and proc, And dont be scared  

BIOS OCing really isn't that complicated. Change BCLK/multiplier for whatever CPU frequency you want... test with something like Prime95 (if voltages are way too low it'll let you know quickly) or a Linpack app like LinX or Intel Burn Test. They are generally faster at finding stability issues. If there are issues, turn up Vcore or VTT by maybe .01V and try again... rinse and repeat.
With your clock at 3.77, you probably have an odd bclk which won't let your RAM run at full speed, by the way.

As to how far you can go, well, you could probably go over 4ghz without stability issues if you push your voltages high enough, but then heat is an issue, and also, you'll probably have to exceed Intel specs for max voltages too. They are vcore: 1.55, Vtt 1.21, PLL 1.98 on the i5 750.

Just fyi, at 200bclk 3.6ghz I currently have it at 1.2 vcore, 1.15 vtt, 1.82pll. At 3.8ghz it goes up quite a bit, 1.28vcore, 1.26 vtt - although I got a fairly stable Prime95 with 1.35 vcore, 1.208 vtt, but LinX wouldn't pass. Possibly at a lower bclk tho, the vtt can stay lower at higher CPU speeds... lots of testing is needed lol.

The question is, how high do you need it to be? At some point you won't see a performance boost in your daily things like gaming and surfing the net - if you run extreme graphics programs for photo and video editing, or high end audio software, then the higher CPU speed might show some value.