Help! Basic advice

YES, nothwithstandind the fact i've been using EWQL for months, and i pretty know that my hardware is very, very bottom level, i have 4 basic question i have never found an answer reading here and all over the net.

Consider i'm composing with a laptop, NO pro soundcard (that i still have to buy, together with a desktop pc).

My sequencer now is REAPER!, that i prefer to cubase LE for the unquestionable less hw resource needed for my poor notebook (compaq nx7400, intel centrino: onecore! less than 2GHz).

I use 1 external harddrive (i haven't understand how to split orchestral parts into 2 hw, given the fact that i copied all the parts from 1 hd to the other: looks like i have to trick ewql disconneting one instance of ewqlso-kompact from reaper, disconneting the harddisk too and than moving it back in online status, ewql-kompact requesting to give the new position for that).

...however, apart from this, and other million question i still have, 2 filosofical ones are tricking my mind:

1-is a pro soundcard needed to have the same bit-by-bit soundwave recorded when i lauch the rendering process, or is it important "just" to have a good sound for my ears, and not a so-so from a common notebook? In other words, the soundcard process the sound to be recorded with VIRTUAL instruments, or just make it be reproduced... very well?

2-Considering my 7200 external rpm harddisk, what limitation can have the process of rendering, when 16-20 instruments are charged? (i have 4GB ram in windows xp, with 2700 MByte set free in bootstrap) I sometimes note some "stop" from some instrument (overload i suppose, as i read here), but with asio diver (directX full duplex is the most stable i found) set 2048 and a high value in ewql-kompact work "fine" IMHO.

3-In the process of rendering:

full loading an instance of kompact could result in a poorer sound? I mean, kompact do give the same resources on every voice, or does it have a "limited" power of processing, APART from the adjustable set-up (ram/n