Your correct in your assumptions, the XP1600+ actually runs cooler than an Athlon 1.4 even though it is rated at the same clock speed, so heatsinks rated at 1.4+ will be OK!
But you carn't overcool so go for something decent like the thermalright SK6, Volcano 7 or 6cu, the new twin pipe Coolermaster HHC-001, Globalwin CAK11 38 or the Monster Swiftech MC 462A, these are all top shelf heatsinks, leaders in there class for serious overclockers.
If you just want to keep it cool without the clocking I can personally recommend Taisols cheap copper insert heatsink, the CGK 760092 at around $16 with 23cfm fan it is a good performer with the heatsink potensial for some serious cooling when pared with a Delta 38, kept in standard trim this cooler is more than enough for an unclocked XP1600+
I have got to finnish by pointing out in addition to a good heatsink/fan how important it is to have additional case fans fitted, it is no good buying a trick heatsink if all you are going to do is blow warm air onto it!
You must have good air turnover in the case to lower the internal air temperature, this is a MUST, don't do it later, do it NOW!
Sorry don't have any experience with water cooling, I have heard that it is very good but necessary? well that depends on you, and what you intend to do with this rig.
My opinion is if you want to run a 1400mhz processor at 1700, then why not buy a 1700 in the first place? Martin Vote if you found this post helpful please!!
