First, why do you want an HR54 instead of an HR44? the only real difference is that the Hr54 can support, via the C61K or using a directv 4K compatible RVU, 4K live transmissions. The extra two tuners (seven vs five) are not usable as regular tuners, they are only there for 4K, and you would need a reverse band LNB to use them, whenever DirecTV starts to use the reverse band for 4K. The Hr54 and HR44 have the same disk size, same speed processors etc The HR54 will only take five of your tuner slots, unless you go to 4K when it will eventually take seven, but then you will have the reverse band LNB which supports 13 tuners anyway.
And just FYI, there are now regular SWM LNBs that support 13 tuners also, if you need the extra tuners at some point.
If you are entitled to a 4K upgrade, and you already have a 4K TV (important!), you can get the HR54 and C61K as a free upgrade from your existing system. If you can't get that upgrade, IMHO you would be better off calling DirecTV, tell them your HR34 has a hard drive issue, sometimes won't even power on, and getting a replacement. 99% probability you will get an HR44. If you get an HR34, send it back, say the picture is pixelating or something.
And the C31 works fine with the HR54 (I have one).