The reason your onboard sound card with ASIO4ALL was working differently was that ASIO4ALL is a DirectX shell that wraps itself around the WDM Driver to give you ASIO connectivity. The Direct X driver is managed by Windows, however it will resample audio to match the need of the application and the needs of the OS making it unreliable for quality audio recordings.
Switching over to ASIO supported audio interface means getting a device that does not use Direct X. ASIO is not supported by Microsoft therefore PC optimizations must be done. ASIO will bypass all kernel mixing operations to give you a clear path to 24 bit audio. Setting your buffers to 64 will most certainly impact even the most powerful systems.
The data path from USB to Direct Memory must be clear of obstructions. You may have other devices on your system that are sharing resources with your USB bus that are interfering with the audio stream.
Consider looking at your system to see if you have an DPC latencies that will affect realtime audio operations. A great tool for that is available here: http://www.thesycon.de/deu/latency_check.shtml
Read up on how to use that tool and how to dial your system in for better ASIO device performance. Most often the biggest culprits for pops and clicks with ASIO's on PCs are the video driver and the network card driver. Check your motherboard manual to find a USB controller that is not shared with another embedded device. ASUS Motherboards always have this in the PCI section of the manual.
If you're still having issues, you can turn to the user forum to get input from others on how they resolve the issue, and/or you can contact us at support.presonus.com so we can see if we can help you further.