Hi, yes you can replace and upgrade the crossover components. Two years ago I bought a pair of Tannoy Edinburgh HE and I had a deception when I opened them. Although the Edinburgh is not the most expensive Tannoy Prestige speaker, they are not cheap (price list arround 6500u$s). The crossover components are bad, cheap from China. Except the foils (they are not the best but they are very good) you can upgrade all. So I replace them and I have excellent results.
1) Capacitors: As Ecclectique, move to Mundorf. For the HF crossover go to the Silver in Oil, and for the LF the Supreme are excellent.
2) Resistors: remove the expotus chinesse resistors and move to Mills MRA12
3) Internal cables: my Edinburgh use the very little Van Den Hul CS-18. I moved to the SCS-12 for the woofer, that it is bigger and better than the SC-18. You will get better, cleaner, deeper and controled bass. For the tweeter move to the SCS-18 or 16, don´t use a cable bigger than 1.2 mm2.
4) Finnaly, if you want, you can upgrade the speaker terminals. I moved to WBT connectors. They are better, easy to connect and easy to attacht speaker cables.
All the upgrades I did, worked. remember that when you replace a component you need a burn in period.