The best overclock chip for the Asus P3V4X is any of the Celeron 2 CPU's. The Celeron-2 633 is probably the best value now. It is well under $100 and the chance of overclocking to 9.5x100 FSB is very good. If you also have good quality, PC133/CAS2 SDRAM, you can run the momory at 133 MHz frequency using the 100FSB/133memory setting. I found this to be the fastest. In fact, it runs faster than the BX board which only allows 100FSB and 100 memory.
If you buy a PIII-700 and plan to run at 133 FSB or above, the P3V4X will not be the optimal board. The BX or 815E boards beat the P3V4X hands down at 133FSB/133memory setting. I would recommend the Asus CUSL2 or CUSL2-C.
The Intel Coppermine CPU is a well designed chip that consumes 17-22 watts full load, dependent on model. With such low power consumption, almost any retail heatsink and fan combination should work fine.
For best value for the money, I recommend the Thermaltake Golden Orb. The cooling capacity is more than adequate and the latch design is extremely well done. It is almost impossible to mount the Golden Orb unevenly against the Coppermine. I cannot say the same for other HSF, including the Alpha.
For the same price, the Thermaltake Chrome Orb has a faster fan, but a conventional spring clip latch. It will cool a little better than the Golden Orb, but it is too big (interfer with the capacitors) to mount in some motherboards, such as Asus CUSL2. It will ideal for the P3V4X with a slotket.
The Alpha heat sink is a piece of engineering art, but expensive. It costs more than twice of the Golden Orb and usually cools no more than 2 degrees C lower than the Golden Orb. If you use a slotket, the Alpha will block some of the SIMM slots due to its height.