Pro Max Tower T2 FCT2250, memory upgrade to 64 GB

Quick question. My pc came with 32GB: 2 x 16 GB, DDR5, 5600 MT/s, non-ECC.  Unit has 4 memory slots. I was considering buying two more of the same cards but Dell recommends  4 of the the 4 x 16 GB, DDR5, 4800 MT/s, UDIMM, Non-ECC, to achieve 64 GB which are 4800 MT/s and the ones I have are 5600 MT/s. My concern is with price of memory being what it is I don’t want to toss the two I have and buy 4 of the 4800 MT/s ones to get 64 GB

Using this pc for music production. I have always had 64 GB in previous 4 x 16 GB, DDR5, 4800 MT/s, UDIMM, Non-ECC set ups. Maybe I don’t need 64 GB? just received the tower today and have not fired it up yet but I would really appreciate any advice….particularly about of mismatch of MT/s (2x 4800 and 2x5600

Thanks so much in advance!