I think that studio computer setups are a very personal thing and obviously everyones priorities are different. But may offer some of my own predjudices!
Bong, you said you want a simple system. I absolutely agree. the more layers of interface you have the more time you have to think about them as opposed to creating music.
I too run a creamware system but tend to have this hardwired in a particular configuration that allows me to
almost entirely work within cubase. The Creamware system is flexible but also takes a while to wrap your head around. I wouldn't bother with a 3 DSP card. I use a 15 DSP card and I can overload even that fairly easily. Also you are limited to the effects and synths on the DSP system as the cards do not run standard VST or other plugins.
I'm not sure why you want o record into Sound Forge then into Cubase (familiarity with SF?). Why not record directly into CUbase. It will sound as good and simplify your work flow.
With regard to monitoring latency: If you monitor cubase audio outputs onto you mixing desk along with direct sound from external hardware there will be a small delay from software/computer - say 10-20 ms. Not ideal. If you route your hardware audio first through cubase, either on individual channels or as mixed stereo pair, and then output to speakers, cubase will compensate for any delays across the board and therefore all tracks should be output time accurate.
If you have enough ins and outs. you can wire your whole studio to the computer , much like a pro tools system, whereby all your external FX can be made to behave like plugins (again latency compensated). Once setup it's easy peasy to operate and you can "save" your entire studio as many times as you like in as many combinations. A creamware system can be flexible within itself but as said before cannot support standard plugins. You'll probably find that the routing allowed within Cubase is completely sufficient for compex routing. All you need is lots of ins and outs.
But this approach requires a level of trust and experience with computer audio systems. If something goes wrong with a hardware setup it is fairly easy to troubleshoot the system i.e. probably a faulty cable. In the world of software drivers, bugs, and system incompatibilities , troubleshooting can be more nerve jangling.
My belly rumble
D