Which Elvis Costello do you want to see – the spiky punk who got banned from Saturday Night Live for playing a song that criticized corporate broadcasting? The elegant musical polymath who dared to say that easy listening maven Burt Bacharach was good? Or any number of Elvises in between? They’ll all be on stage at CMCU on Wednesday. Sure, this is a nostalgia gig, but Costello is one of the best songwriters of this or any generation, and his aim will always be true.