The Pioneer DVR-S201 is the ultimate PC DVD-R burner for compatability. It uses more expensive DVD-R authoring (not DVD-R general) discs. It is however very expensive compared to today's budget DVD-R burners at £3,000+ here in the UK.
You're going to have a tough time finding one, and as vonhosen pointed out, it will be expensive. SCSI certainly won't provide any advantage as far as speed. If you are doing this because you have used up both master and slave locations on your two IDE controllers (i.e., you already have four CD/DVD/hard disks), then you might consider getting another IDE card and putting that in your computer and then attaching the IDE DVD to that.
I run a Pioneer A06 IDE DVD burner in a Firewire enclosure. One of the advantages to this is that I can easily move it to any machine in the shop and burn to it. It works great and Firewire is easily fast enough to keep up with the required data rate. I haven't burned a coaster yet.
With Firewire and USB 2, most of the need for SCSI to connect fast external devices has gone away. The remaining use for SCSI -- providing a super fast interface for really fast disk drives -- has become a niche market, mostly for servers and really high-end workstations. SCSI, therefore, has disappeared from the desktop. This is a good thing IMHO. I have many hundreds of dollars in SCSI cables lying around, each with different connectors (three different connector standards). I always had problems remembering to terminate (or not), forcing multiple reboots ... arrgghh!