If so, neither the LCA's nor the rear lower tie bar are necessary. They don't do a whole lot by them selves as far as performance goes. But, new installing new LCA's with new suspension generally makes the installing job easier. For the 5th gen civics, aftermarket LCA's provide a mounting hole for rear swaybars. But, going by your user name, 6th gens have mounting holes in the factory LCA's so aftermarket ones aren't really necessary.
You don't need them. If you want them for aesthetics, go for it. Just don't buy cheap LCA's.
LCA's should only cost around 2-250. Rear lower tie bars don't do anything and are a complete waste of money unless you like wasting money on cosmetics that serve no purpose. That money can be used towards something that looks more appealing IMO. Retrofits, OEM Si / CTR front upper grill, front lip, etc.
If you want bling that serves a purpose, get an ASR rear subframe brace. Of course it doesn't really do it's job if you don't have a 19+mm sway bar, so you could get one of those too .
I believe I bought my sway bar off jdmland.com. Mine is an USDM OEM ITR 22mm. Then I got my ASR brace off weaksauceparts.com. You'll need end links too. I currently have Blox spherical adjustable ones I bought from JHPUSA. They're like $25+shipping but I have Hard Race ones I've been meaning to put in.