Welcome to these forums !
I'll assume you only want to cool your CPU down, for now.
Your goal is silence, nice, and good luck, this is doable but expensive as i can attest. But it's a great experience
(we share the same goals...)
About the pump: i've been using a Hydor L30 for 1 year and half. I found it was too noisy under load. And had to change the shaft once. So i'm not 100% satisfied with it. I'll compare with a Eheim soon....
1 - false. Even straight watercooling is quite 'powerful'. The D-Tek HC has more surface area and less restriction than the BiX. Since you have no room constraint (where the BiX shines) go with the HC. With straight WC the only thing that has influence on temps is the rad... So a better rad will magically give you better temps.
2 - A res is easier to maintain indeed. But if you don't wat to go to extremes, consider a simple airtrap. Use a small 40mmx50mm PVC section with end caps for example. Look at Turbokeu's setup in this very forum (look for threads started by him). I found this more elegant than a big reservoir, and more practical than a T line.
3 - Not exact. Put the fill point (or airtrap) at top of the circuit - ideally sticking out of the top of the case, with a nice cap - for easy maintenance. Ah don't forget the 'purge' T+valve at bottom ...
Very useful as well.
4 - Bottom front, sucking air from outside (ie the fan is inside). This location because you won't have any bubble problem (they tend to get trapped in rads) and sucking air because axial fans are more efficient that way.
5 - yes, considering you won't place your HC at top where it would act as an air trap...
6 - For my config: 3 waterblocks, Tbird 1000 @ 1500 with FSB @200, Geforce2 and NForce2 all watercooled then, with a single D-Tek HC, a low-speed Papst 4412 N/2GL cools my cpu down to 37-39°C with 22°C ambient. It's rated at ~57 CFM. I think i can even lower the voltage and keep my system stable.
The Papst can be had for ~$23 plus shipping and it's the best 120mm fan i know of (considering performance/noise ratio). It's rated at 26dBA at full speed.
Have fun ! And post photos...
(edit) hmm given the case you have.. you can fit the HC above the PSU, then have its outlet go to the airtrap which would be placed higher, since it would stick out of the top of the case...