Turning HPET off will improve your DPC numbers, but I never saw any improvement in real-world use of Nuendo/Cubase - even with fairly heavy projects recording many tracks with a 32 sample buffer setting. I’ve also heard that leaving HPET on could possibly improve MIDI timing etc., so there is some conflicting information out there about this. Maybe things have changed with the newer chipsets, or the fact may be that I would be better off with HPET turned off, but I never saw any improvement other than lower DPC numbers.
Also of interest - I just recently tried turning off HT on my i7 930 machine and the performance actually improved a bit. Back when N5 first came out I was fighting some CPU spiking issues and tried HT on and off with no resolution of the issue, so I just left it on as the DAW benchmarks always indicated performance was better with HT on. Lately, I’ve been seeing SB state that HT is NOT supported and read a post or two about some seeing performance improve at low latencies with HT off. Interestingly, I’m seeing slightly better performance even at 512 sample buffer settings though I need more time to assess the performance differences, so the jury is still out for me about these things.