Being as a month has gone by since you posted this, you no doubtedly have your system together, but I feel everyone is entitled to the common courtesy of a response & I may be able to offer some helpfull info. I am not inclined to offer advice on things I am not familiar with but I have a fair amount of knowledge & experiences in dealing with thermal systems of many different types & ranges & being one who can never leave anything the way it was made, I had to see what the 620 was capable of on my system... & to prove a point if to no one else but myself.
Just use the cpu pin, but do not connect the fan to the lead off the pump. Instead hook the fan to either a sysfan header or dirrectly off you psu 4-pin conn. You will really want the stock antec fan runnin 100%, otherwise it will not cool well at all, trust me..
Set the cpu fan control to either 50c auto or just 100%. This will not change the pump speed, it only controls how much juice is feeding the pump. Pump speed will vary from 1330-1380rpm.
There are a few main factors that really effect the performance of any cpu cooling system: thermal dissipation into the plate from the cpu, the ambient temp, the total mass & thermal absorbtion of the cooling medium, thermal dissipation capabilties of the radiator, & how much air mass passes through said cooler over a given time & how evenly that airflow is distributed over the exchangers surface area. The only of these you really have control over is the latter items.
Now, that being said, decide how good you want this system to perform, or how cool you realy want your cpu to be. I have done a fair amount of testing with the 620 in my system & let me tell you there is a tremendous amount of headway to be made over the stock fan set-up.
I recomend ditching the 120x25 fan a use it as an auxilary sysfan elsewhere in your system. What you want to get is a 120x38 unit with a minimum of 100cfm free flow at max voltage. This will ensure you have more than adequate air mass flowing through the heat exchanger when you start leaning on it hard. The bigger, the better, in this case & use your add on fan controler (make sure the controler can handle the amp draw of these larger fans) to control the fan speed as needed for your desired cooling results. Yes it is an added expense, but much cheaper than the next best alternative, an H80, but at almost twice the cost of the 620, $11-22ea. is a small price to pay for the benefits gained. I would actually recomend that this approach be used even on said H80. This is due to the fact that the shorter 25mm housings lack the plenum volume/ blade height & resultant surface area (force over an increased surface area) to overcome the increase in flow restriction, & change in static flow caracteristics, present through the heat exchanger. Every manufacturer that supplies a 25mm fan in these systems is shooting themselves in the foot because if they did use the thicker fans, the performance & subsequent reviews of their systems would be much improved & their sales would no doubt follow suit...
If you want max cooling & the quietest opperation, pop for two. Then you can turn them way down (less noise) to achieve the same or better performance. This also gives you a broader cooling range than having a single fan.
I use a scythe ultra kaze 3000 (do a search if you are not familiar with it). It flows 133cfm @ 3000rpm & runs at about 46dba on max. It is a sleeve bearing fan. It can be had for as little as $11ea on ebay, shipped!
If you want a longer life unit I would humbly recomend the Adda 3000 or 4000 rpm fans. They are noisier than the scythe unit, according to factory specifications. The 3000 unit flows 120cfm & the 4000 is rated at 200cfm. The latter is over 60dba, but two of those bad boys would no doubt get the job done!
As an axample of what the 620 system is capable of, I am running my i7-860 @ 3.9ghz (&everyone supposedly knows how innefficient they are @ those clocks) & my cpu never gets over 60C (54-57C is the norm) @ 100% fan speed running games for hrs on end as well as running any benchmark software. Idle is in the low to mid 30s, depending on the core. Stock, 25-27C idle, 47c max running prime95 for 16hrs, & the nominal temp hovers around 44C This was @ 100%cpu usage & 99%max frequency, so I was not going easy on it. This is with one fan & my ambient is around 68F. In most cases I have found 50% fan speed to be quite adequate at clocks around 3.6Ghz. I will be testing dual fans very shortly.
If I can be of any more assistance, don't hesitate to ask & in short, don't hesitate to buy the 620 as in my opinion, when properly set-up, it is the best bang for the buck, along with an H60 (best buy still carries them) on the market.
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