Welcome:). Get Kprobe2.4.2 and go to the toolbar and 'info>drive'. Let that run a second, then scroll down to the bottom and see what your burst rate is. It should be 22mb/s, but you may get away with 12mb/s...I did for quite a while with my 851@832 and my laptop and burning at 8x. I am glad you are not multi-tasking as that will help.
If the burst rate is OK, then you may benefit from defragging often and having 5+GB free continuous space on your HDD for ripped images. You may also want to make sure your HDD has its DMA enabled and your 'current transfer mode' in 'device manager' is 'ultra DMA mode 2' or higher...for a HDD UDMA4 or UDMA5 is common. One more thing I would recommend. With a big and power-hungry CPU like yours, I might suggest you stay plugged into an AC outlet, as your laptop on DC/battery may throttle down during burning.
You will also be able to use kprobe to check your burn results with BLER scans(scanned at 4x scan speed the forum standard for comparison). You can read Interpreting PI/PO error scans to find out what these graphs mean. PI/PO is now referred to as PI/PIF. Roughly, PImax<280; PIFmax<4. Attaching disc quality scans to your post of any problem discs will help us help you.
As for regretting the external burner...I think you might be happier in the long run as most laptop dvd burners today are slow(er) and get less firmware support resulting in lower quality burns IMHO
Let us know if any of this works for you.