Welcome:). Do you notice buffer underruns when you are burning? Are you doing any multi-tasking when you are burning? If you are multi-tasking, try a burn without doing anything else and see how that goes. You also might benefit from defragging your HDD often, as fragmented source files can lead to buffer underruns and slow, poor quality burns. You can also check to see if your source HDD is also at UDMA5 or 6. Another potential problem could be your HDD and your burner on the same IDE channel, like HDD-PRI-MASTER and your 1673 as PRI-SLAVE. If this is the case, try your 1673 as SEC-MASTER.
Is this the time for the full burn only, or have you selected ‘verify data on disc after burning’ and the 15 minutes includes this time? If this includes ‘verify’ time, then you are OK. If this time is for the full burn only, try installing this nero ‘show actual speed’ hack . This will tell you the…um…actual speed of the burning in real time, so you can see if the burn attempts to shift up to faster speeds or whatever. 15 minutes is what time a 4x burn takes.
Also, you can check your burn results with Kprobe 2.4.3 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 the offending discs will help us help you. The scans may tell us what is happening.
Let us know if any of this helps.