Good for street vs. track depends upon the gear-set and final drive you install. Now if we were instead talking about dog-boxes, your point of view would be spot on. The E153 is a 5 speed transmission. Once you get into the power range where people are tempted by a E153, the penalty of losing a gear is less severe. The local tracks are tight enough that I never see 6th gear. I have heard there are tracks out in other areas where people do make use of 6th gear on their c64 transmission.
Storm titanium 2005 Elise with carbon fiber spoiler, BWR sway bar, BOE toe links, gPan2, LidBone, sector 111 wheel studs, Grey RAC Monolite wheels with toyo R1R, Team Dynamics 1.4 with Hoosier A6/R6s, Katana2 Supercharger, ECU with 265 flash. PPE headers w/decat, CEL angle eliminator, Silent touch catback, Rear Panel Eliminator, HKS intake, V2 fuel tank, Walbro255 fuel pump. HID lights.