for the same price?.......NO!
a decent 240 rad cost 50-75% of the H-100
a decent CPU waterblock cost 75-100% of the H-100
you still need hose, pump, fittngs, and other misc stuff, so no, you can't!
but if you choose to spend alittle more you can get better cooling with a DYI kit.
I kinda did the same as you, took my 3.2 Ghz CPU up to 3.6 on air. It wanted to go higher but the temps was more than I wanted to see.
On day while cleaning the dust off the stock CPU cooler a fin broke off the fan, causing it to shake like crazy and it gave me a "CPU FAN ERROR"
Off to the store I went to get a cheap tower style cooler , for $20 i could get a no name brand one, or for $59 i could get a h-60. I decided to give the h-60 a try. took it home ,installed it,temps were wose, changed out the thermal compound and reseated it, temps went way down!!
I was able to push my overclock another 200Mhz to 3.8Ghz with more volts and it never got to 70 C. I hit the ceiling of the CPU and motherboard before the h-60 gave up on cooling.
for my new build I was gonna go with the H-100 but later decided to go full water cooling. I bought a 240 rad , hose, fans and some coolant, for 50% more than what a H-100 cost, and still need a water block, pump and res.
I one day I decided it was a waste having all this sitting around, and not using it, so I bastardized my H-60. I put the 240 rad on my H -60 block/pump unit. My current CPU is running at 4.255Ghz at 1.35volts(prety much as much as I want to push it)and it never sees 60 degrees.
the good thing about the H-100 is you buy it,install it,forget it. One low purchase price and cooling is done. the bad thing is you can't add to it and if it breaks you have to repace the whole thing. If your temps are higher than you want all you can do to it is add more fans or higher CFM fans(more noise)
a pieced togeather kit cost more cause there are more bits to buy, but I think it's worth it. You get all the bits you want, and if something breaks, you change your system, or made a mistake, it's easy to change one part or add another to the system. once you get it up and running if your temps are too high add another rad! If you want to add in your video card, its easy too do!
Although a pieced togeather kit isn't always garranted to perform better(or like) a H-100 you would really have to mess it up for it not too. But you can easily change something and play with it to make it better, unlike a H-100.