Start with the stock cooler (my X2-4200 came with the heatpipe model), and see if you can live with the noise. The cooling performance is actually really good for an OEM cooler using stock TIM.
If it is too noisy, or you want serious OC action, look into upgrading.
If you upgrade, suggested coolers are:
-XP-120/XP-90
-SI-120
-Big Typhoon
-Scythe Ninja (with or without fan)
If you go watercooling, don't buy a "basic" kit. Most kits have equivalent performance to the above coolers. See X-Bit labs for some recent cooler reviews.