Looking for brighter tubes

Attention tube heads: I'm looking for brighter (more treble...not higher amounts of glow and chrome) tubes, if they exist. My amp (Jolida JD502P) has a well regarded bunch of Russian Tung Sol 6550s and 12AX7/12AT7s but I'm wondering if there's anything out there that imparts more sizzle in this amp. I do like the amp as it is...but hey..."rolling rolling rolling, keep them tubeys rolling...