As Badger0-0 points out, the Center is the key. Having a reasonable tonal match across the front is pretty important, though how well you will personally tolerate a mismatch is something only you can determine.
However, moving up to floorstanding in front for now, then adding the matching Center at a later date would be a reasonable path to folllow for upgrading. While Center speakers aren't free, neither are they excessive in price.
The Dali Zensor Center is about £229 and the Monitor Audio Bronze BX Center is about £150. Those should be attainable within a reasonable period of time.
Again, you can determine for yourself how much the mismatch bothers you. If you are OK with it, then fine, and if not, you do have options available to you.
Steve/bluewizard