Your HT guy is right that the front 3 speakers should be timbre matched. You should go with the same brand for the front 3 speakers. But getting 3 of the same speaker is totally unecessary overkill. Just make sure that your center speaker is the same brand as your L and R fronts and timbre matched to them. And I don't think it is necessary to get the same brand surrounds as your fronts. It is probably best, but not necessary.
If I were you, I'd get some pretty good L and R fronts, a lower priced but timbre matched speaker in the same brand as your center, and then either (1) whatever value consious surrounds the speaker maker itself recommends from its line-up, or (2) some different brand surrounds that will match well with your fronts. Heck, if you told the speaker maker that you will not under any circumstance buy their surrounds because of your budget, they might even tell you what less expensive speaker they'd recommend to match with the fronts you are buying from them. Maybe they would not, but they might and it does not hurt to ask.
And, I assume it goes without saying that you should listen to as many speakers as you can before you decide on anything your HT guy recommends. At least that way you will know if you agree with his recommendations.
If I were you, I'd get some pretty good L and R fronts, a lower priced but timbre matched speaker in the same brand as your center, and then either (1) whatever value consious surrounds the speaker maker itself recommends from its line-up, or (2) some different brand surrounds that will match well with your fronts. Heck, if you told the speaker maker that you will not under any circumstance buy their surrounds because of your budget, they might even tell you what less expensive speaker they'd recommend to match with the fronts you are buying from them. Maybe they would not, but they might and it does not hurt to ask.
And, I assume it goes without saying that you should listen to as many speakers as you can before you decide on anything your HT guy recommends. At least that way you will know if you agree with his recommendations.