Hi there
Perhaps you have already solved your problem, but if you haven't here goes.
In your post you have not detailed the Dell XPS computer. Is this a Laptop or Desktop? It is important to understand what each piece has, and what is required to make this process work. I'll assume this is a Laptop, (although most of this applies to a desktop as well) so here's what you need to look for to make this work. In most cases the laptop is irrelevant since it is the sound card taking most of the load and transferring the data to the hard drive. The CPU is hardly doing anything except providing you a visual of what might be going on.
Before we start understand that Presonus ships the unit with all the necessary drivers including ASIO that are optimized for the 1818 and all the rest of the audio devices they sell.
#1 How many Hard Drives are on the Laptop?
#2 Internal Hard drive speed (only a 7,200 RPM drive will work) NOTE! a 5,400 RPM Hard Drive will not work!
#3 Try Turning off the (Use MultiProcessor Engine) in Sonar (some Laptops will not sync correctly and you will have dropouts galore)
#4 You must setup the first Hard Drive for the OS (Operating System) This is also where you must install Sonar Software.
#5 The second hard drive must be a 7,200 RPM formatted hard drive and within Sonar you must tell Sonar that this is the hard drive where all the audio files will be streamed to when recording, and from when you want to play back what you recorded.
If you do not use this method on yor system all the latency issues you describe will never be workable. Pay special attention to the Esata I discuss here because it is the only solution that works!
I have 3 laptops that I use for live recording and they all have different mixers attached to them.
The first one is the oldest being a 1999 HP running on Win XP that has 1 internal 100 GB, 7,200 RPM dive and a 2 TB, 7,200 RPM external drive that is connected via a Esata card (and not USB because USB and Firewire hard drives will not work). The Esata protocol operates @1.5 GHZ per second instead of 480 MB per second so the thru-put is 3 times faster than USB 2.0 and it is a true bidirectional @ this speed. USB is also Bidirectional but divides the 480 MB per second (240 MB in and 240 MB out). These are the kind of things that cause bottlenecks for audio. My HP is connected to a Mackie Firewire 1604 mixer but will work with any USB i have it connected to. It records 18 tracks without a hitch for hours on end.
My second machine is an Acer 20" Laptop built in 2005 running on Win XP that uses 7,200 RPM boot drive and is also connected via a ESATA (PCMCIA CARD) connected to a 24 channel Presonus and records 32 channels without a hitch. I usually record each set as a song and then back at the Studio I'll separate each song so the computer can manage the data more efficiently. I will take only the drive that has the Sonar data on in, connect it to the desktop and away I go. Absolutely no issues.
The third machine is a newer HP running on Windows 7 connected via a USB Motu 828 MK111 and again no issues since we use the Esata.
I've provided three machines that all use USB 2.0 or Firewire audio and they all work with any sound card. The issue is not the sound card as much as it is how the data is being streamed to the device that saves the audio data. If you have a funnel like effect due to the hole in the funnel being too small eventually the contents overflow and so will your audio. Since it has no where to go some of the data spills over and an interruption of data occurs causing a dropout. But, it's not the audio cards fault (usually) it's how much data can be stored on the hard drive that causes the issues!
My main studio computer has 7 additional PC's connected to the host via Ethernet. The host has 6 internal hard drives and 2 external hard drives via an ESATA protocol. This system is 4 years old has 16 gb of Ram and runs on Win 7 64bit. After the field recording is finished (on the Laptop) we connect the hard drives that were used to capture the live band recording and continue producing them in the studio. This setup has never had any issues and uses a 2 sound card approach. There is a PCi card MaXiO 032e from ESI-Pro that the speakers are connected to, and a second Firewire 24.4.2 Presonus 24 channel mixer that I use for recording in Sonar (mics are connected to the mixer and all 24 channels are live). The SPDIF output is routed to the Maxio 032e and everything works perfectly. Full monitoring with effects is available in real time with absolutely no latency or hiccups-ups of any kind since it was assembled.
Hope this helps you.