Audio Research Dual 75A or SP9mkii pre

I am in the verge to upgrading my front end to tubes. I currently have all SS, B&K ST2140 and a Rotel RC-970BX with the Energy Veritas 2.2. I mostly listen to rock and country and occasionally vocals and acoustics. So my question is, should I get all tube or mixed? I am able to get one or both. Thanks

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Get both! Classic ARC gear is always desirable! I have an SP6 and a D75. Bought together several years ago from an eBay seller. He provided a set of KT120's in the D75. 

Thanks for the response. I am more inclined in the SP9 for tube/SS combination with the ST2140. I just concern with maybe a mismatch.