just playing devil's advocate but all we know from press release is that the v cache chips are coming in Q1 next year...they could announce in jan for feb release date or march, or maybe beginning of jan, we don't actually know and that's possibly a 4 month wait...and then performance 15% gain on current 5000 series...is that back up with alderlake so parity? can't remember top of my head, and pricing? we don't know that yet either...so if went with alderlake you could have it now, you don't have to wait..
a ddr4 z690 is more expensive, but that's really the only cost difference really compared to a B450 board..you'll still have to buy ddr ram. and a b450 board is pcie3 only, incl the gpu slot...z690 board is pcie5 gpu slot(irrelevant at mo but it's there, and next years gpu's are meant to double todays throughput)...the tomahawk ddr4 board(taking this as my example at £259) can also take 4 pcie4 nvme's...b450 can take none, and if you compare to a b450 tomahawk max, it can take 1 pcie3 nvme. I'd take the vrm's on the z690 tomahawk over a b450 board...from what I read, a lot of them were poor(someone posted a list..wasn't pretty reading)
I'd say the z690 board is more equivalent to a X570 board no? and most of those only take 2 nvme, and are similarly priced to the z690's....x570 tomahawk down at £179 now, but few months ago was £230..same with ram..when I bought in jun, sammy b die 32gb was over £300, corsair 3600c18 over £200, the crucial ballistix 3600C16 was £190 and out of stock
Just saying modern cpu wont be a bottleneck for foreseable future, it'll be the gpu, so if you went alderlake route, cpu is powerful enough you wont be upgrading in a year or so, it'll do you fine, and with pcie5 for your gpu, you can upgrade that 1st and you'll still have a gaming rig. AM5 is due end of next year, and I guess that'll be pricey too. Online saying DDR5 wont become mainstream till 2023/2024 so still life in ddr4 boards yet
then again, black fri might see great sale prices on existing kit, which makes everything change again. very happy with my b550 board and 5800X