Sure you can.
The easy way is to look for a pre that has an HT pass-through (a/k/a unity gain pass through). It takes the front L & R analog feeds from your processor and sends them on to the two channel amp as usual, without effecting gain. This keeps your carefully matched gain levels intact.
If your pre doesn't have a pass through, you could carefully check levels with an SPL meter while setting up the multichannel playback. Note the setting on your pre's gain control that works and always put it there for multichannel play. Less precise than a pass through but maybe good enough?
I dont know whether either of the pre's you're considering has a pass through but I'm sure you could find out easily enough.
The easy way is to look for a pre that has an HT pass-through (a/k/a unity gain pass through). It takes the front L & R analog feeds from your processor and sends them on to the two channel amp as usual, without effecting gain. This keeps your carefully matched gain levels intact.
If your pre doesn't have a pass through, you could carefully check levels with an SPL meter while setting up the multichannel playback. Note the setting on your pre's gain control that works and always put it there for multichannel play. Less precise than a pass through but maybe good enough?
I dont know whether either of the pre's you're considering has a pass through but I'm sure you could find out easily enough.