Since we're talking investment-
HD 650- $291 (Senn Black Friday sale 2012)
Crack + Speedball (SB free from that site) $279
TS-5998 tube $65 (because I'm a boss)
Tung-sol 12AU7 tube $19 Ebay
Total $654. Wow when I break it down like that, that makes me exceptionally happy considering I haven't even felt the slighted itch of upgraditus in almost a year.